UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K

000-31311

(Commission file number)

PDF SOLUTIONS, INC.

(Exact name of registrant as specified in its charter)

(408) 280-7900

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

Common Stock, $0.00015 par value

     Indicate by check mark if the registrant is a well-known seasoned issuer (as defined in Rule 405 of the Securities Act). Yes o No þ

     Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes o No þ

     Indicate by check mark whether the Registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes þ No o

     Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.    o

     Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, or a non-accelerated filer. See definition of “accelerated filer and large accelerated filer” in Rule 12b-2 of the Act (Check one):

     Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). Yes o No þ

     The aggregate market value of the voting stock held by non-affiliates of the Registrant was approximately $172,265,642 as of the last business day of the Registrant’s most recently completed second quarter, based upon the closing sale price on the Nasdaq National Market reported for such date. Shares of Common Stock held by each officer and director and by each person who owns 5% or more of the outstanding Common Stock have been excluded in that such persons may be deemed to be affiliates. This determination of affiliate status is not necessarily a conclusive determination for other purposes.

     There were 26,652,844 shares of the Registrant’s Common Stock issued and outstanding as of March 10, 2006.

DOCUMENTS INCORPORATED BY REFERENCE

     Part III incorporates information by reference from the definitive Proxy Statement for our Annual Meeting of Stockholders to be held on May 24, 2006.

TABLE OF CONTENTS

PART I

      Some of the statements contained or incorporated by reference in this Annual Report are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. Words such as “will,” “anticipate,” “continue,” “could,” “projected,” “expects,” “believes,” “intends”, and “assumes”, the negative of these terms and similar expressions are used to identify forward-looking statements. These statements are made based upon current expectations and projections about our business and the semiconductor industry and assumptions made by our management are not guarantees of future performance, nor do we assume any obligation to update such forward-looking statements after the date this report is filed. Our actual results could differ materially from those projected in the forward-looking statements for many reasons, including the risk factors listed in, Item 1A, Risk Factors. All forward-looking statements in this report are based on information available to us at the date of this report and we assume no obligation to update any such statements.

      The following information should be read in conjunction with the Consolidated Financial Statements and notes thereto included in our Annual Report. All references to fiscal year apply to our fiscal year which ends on December 31.

Business Overview

      Our technologies and services enable semiconductor companies to improve the yield and performance of integrated circuits, or ICs, by integrating the design and manufacturing processes. By providing our customers the ability to quickly characterize and model their manufacturing processes, our customers can improve the capabilities of their manufacturing processes faster and design products that are more manufacturable. We believe our solutions improve a semiconductor company’s time-to-market, yield, and ultimately product profitability. Our solutions combine test chips to characterize a manufacturing process, a proprietary electrical wafer test system, proprietary yield modeling and simulation software and methodologies, design-for-manufacturability (DFM) software, yield management system (YMS) software, and professional services. As an integral part of IC design process development, and fabrication, our solutions enable our customers to analyze yield loss mechanisms to identify, quantify, and correct the issues that cause yield loss. This drives IC design and manufacturing improvements that result in an optimized yield ramp to achieve and exceed targeted IC yield throughout process life cycles. Our solution is designed to increase the initial yield when a design first enters mass production, increase the rate at which that yield improves, or ramps, and achieve higher final yield during volume production. In addition, a yield ramp completed with our technologies allows subsequent product designs to be added to the manufacturing line more quickly and easily.

      The result of implementing our solutions is the creation of value that can be measured based on improvements to our customers’ actual yield. We align our financial interests with the yield and performance improvements realized by our customers, and receive revenue based on this value. To date, we have sold our technologies and services to semiconductor companies including leading integrated device manufacturers, fabless semiconductor companies, and foundries. The key benefits of our solutions to our customers are:

      Our objective is to provide the industry standard in technologies and services for integrating IC designs and manufacturing processes. To achieve this objective, we intend to:

Industry Background

      Rapid technological innovation, with correspondingly short product life cycles, now fuels the economic growth of the semiconductor industry. Previously, companies could afford to take months, or years in some cases, to integrate new IC designs with manufacturing processes. With historically longer product life cycles, IC companies ramped production slowly, produced at high volume once products hit their prime, and slowly

reduced production volume when price and demand started to decrease near the end of a product’s life cycle. Now, companies often need to sell the most volume when a product is first introduced and has a performance and pricing advantage over its competition, or they will lose the market opportunity and the related revenue.

      Increased IC complexity and compressed product lifecycles create significant challenges to achieving competitive initial yields and optimized performance. For example, it is not uncommon for an initial manufacturing run to yield only 20%, meaning 80% of the ICs produced are wasted. Yield improvement and performance optimization are critical drivers of IC companies’ financial results because they typically lead to cost reduction and revenue generation concurrently, causing a leveraged effect on profitability. Historically, yield loss resulted primarily from random contamination in the IC manufacturing process, for example from particles falling on the wafer during the manufacturing process. As the semiconductor industry moved to 130-nanometer process technology and beyond, the dominant factor of yield loss with nanometer-era ICs has shifted from contamination to:

      Semiconductor manufacturers have traditionally addressed systematic and performance yield loss reactively and almost exclusively by trial-and-error adjustments to the manufacturing process during volume production, an inefficient and time consuming approach.

      Disaggregation of the semiconductor industry has further complicated IC companies’ ability to minimize systematic and performance yield losses. Historically, leading semiconductor companies designed, manufactured, and tested their ICs internally, thus retaining process-design integration know-how. Today, the industry is comprised of separate organizations, as well as separate companies, that specialize in a particular phase of designing and manufacturing ICs. This has fragmented the knowledge related to the integration of IC design and manufacturing and resulted in great difficulty in making designs compatible with a manufacturing process prior to volume production.

Technology and Intellectual Property Protection

      We have developed proprietary technologies for yield simulation, analysis, and improvement. We continually enhance our core technologies through the codification of knowledge that we gain in our solution implementations. Our technology includes:

      Our future success and competitive position rely to some extent upon our ability to protect these proprietary technologies and to prevent competitors from using our systems, methods, and technologies in their products. To accomplish this, we rely primarily on a combination of contractual provisions, confidentiality procedures, trade secrets, and patent, copyright, and trademark laws. We license our products and technologies pursuant to non-exclusive license agreements which impose restrictions on customer use. In addition, we seek to avoid disclosure of our trade secrets, including requiring employees, customers, and others with access to our proprietary information to execute confidentiality agreements with us and restricting access to our source code. We also seek to protect our software, documentation, and other written materials under trade secret and copyright laws. As of December 31, 2005 we have been issued 22 patents worldwide, which includes 11 U.S. patents, and we have 55 patent applications currently pending worldwide, which includes 21 pending in the United States. We intend to prepare additional patent applications for submission to the United States Patent and Trademark Office and various foreign patent offices. In the future, we may seek additional patent protection when we feel it is necessary. Characterization Vehicle^®, Circuit Surfer^®, CV^®, Optissimo^®, pdFasTest^®, pdFab^tm, PDF Solutions^®, Proxecco^®, the PDF Solutions logo, WAMA^®, Yield Ramp Simulator^®, and YRS^® are our registered trademarks, and dataPOWER^tm, Design-to-Silicon-Yield^tm, pdCV^tm, and pDfx^tm are our trademarks.

Products And Services

      Our solutions consist of integration engineering services, proprietary software, and other technologies designed to address our customers’ specific manufacturing or design issues. These solutions can be grouped as follows:

      Manufacturing Process Solutions. IC manufacturing process development typically involves four sequential phases: research and development to establish unit manufacturing processes, such as units for the metal CMP or lithography processes; integration of these unit processes into functional modules, such as metal or contact modules; a yield ramp of lead products through the entire manufacturing line; and volume manufacturing of all products through the life of the process. We offer solutions targeted to each of these phases that are designed to accelerate the efficiency of yield learning, by shortening the learning cycle, learning more per cycle, and reducing the number of silicon wafers required. Our targeted offerings include:

      Design-for-Manufacturability (DFM) Solutions. Our DFM solutions are designed to enable our customers to optimize yields within the design cycle before a design is sent to the mask shop to more quickly and cost-effectively manufacture IC products. We target these solutions to customers’ requirements by providing the following:

      Our solutions incorporate the use of various elements of our software and other technologies depending on the customers’ needs. Our software and other technologies include the following:

      Characterization Vehicle (CV) infrastructure. Our test chip design engineers develop a design of experiments (DOE) to determine how IC design building blocks interact with the manufacturing process. Our CV software utilizes the DOE, as well as a library of building blocks that we know has potential yield and performance impact, to generate CV test chip layouts. Our CVi includes:

      Yield Ramp Simulator^® (YRS^®) Software. Our YRS software analyzes an IC design to compute its systematic and random yield loss. YRS software allows design attribute extraction and feature-based yield

modeling. YRS software takes as input a layout that is typically in industry standard format and proprietary yield models generated by running our CV test chips. YRS software is designed to estimate the yield loss due to optical proximity effects, etch micro-loading, dishing in CMP, and other basic process issues.

      Circuit Surfer^® Software. Our Circuit Surfer software estimates the parametric performance yield and manufacturability of analog/mixed-signal/ RF blocks in a design, such as RF transmission, PLLs/ DLLs and logic critical paths. Using our Circuit Surfer software, a design engineer is able to estimate how manufacturing process variations will impact circuit performance and yield and then optimizes the circuit to reduce or eliminate the impact of those variations.

      pDfx^® Environment. Our pDfx environment improves the manufacturability of ICs by providing process-aware DFM. The environment incorporates our pDfx yield models and software into commercial Electronic Design Automation (EDA) tools available to the IC Design community. These tools are either developed by PDF or frequently in partnership with commercial EDA vendors. Incorporating our pDfx modeling capability into the design flow allows designers to optimize yield, performance, power, and area trade-offs within the design flow before the IC is released to manufacturing. In this manner, customers can further optimize designs for yield within their specific guidelines.

      dataPOWER^tm YMS Platform. Our dataPOWER YMS platform collects yield data, stores it in databases, and allows product engineers to identify and analyze production yield issues using proprietary yield analysis software tools. dataPOWER software contains powerful visualization and reporting tools that are flexible to address customers’ requirements. Our YMS platform is designed to handle very large data sets, to efficiently improve productivity, yield and time-to-market at our customers’ sites. Optional modules extend the base platform to enable defect analysis (dP-Defect), memory analysis (dP-bitMAP) , spatial signature analysis (dP-SSA), and optimization of die on the wafer (dP-shotMAP).

      With the exception of dataPOWER and pDfx, the primary distribution method for our software and technologies is through our manufacturing process solutions although, we have in the past and may in the future separately license these and other technologies. Though dataPOWER and pDfx are primarily licensed separately, they are also distributed within our Design-to-Silicon-Yield solutions.

Customers

      Our current customers are primarily integrated device manufacturers (IDMs), but also include fabless semiconductor design companies and foundries. Our customers’ targeted product segments vary significantly, including microprocessors, graphics, memory and communications. We believe that the adoption of our solutions by such companies validates the application of our Design-to-Silicon-Yield solutions to the broader semiconductor market.

      Texas Instruments, International Business Machines Corporation, Matsushita Electric Industrial Co., and Toshiba Corporation represented 15%, 13%, 11%, and 10%, respectively, of our total revenue for the year ended December 31, 2005. Toshiba, Sony Corporation, Matsushita, and Texas Instruments represented 17%, 13%, 12%, and 10% respectively, of our total revenue for the year ended December 31, 2004. Toshiba, Sony, Matsushita and Epson Corporation represented 25%, 15%, 13% and 11%, respectively, of our total revenue for the year ended December 31, 2003. No other customer accounted for 10% or more of our revenue in years 2005, 2004 and 2003.

Sales and Marketing

      Our sales strategy is to pursue targeted accounts through a combination of our direct sales force and strategic alliances. For sales in the United States, we rely on our direct sales team, which primarily operates out of our San Jose, California headquarters. In Japan, we use our direct sales team. In Taiwan and China we use J.I.T. International Co., Ltd. as a sales representative and in Korea we use Acetronix Co., Ltd. as a sales representative. We expect to continue to establish strategic alliances with vendors in the electronic design automation software, capital equipment for IC production, silicon intellectual property and mask-making software segments to create and take advantage of co-marketing opportunities. We believe that these

relationships will also serve as sales channels for our Design-to-Silicon-Yield solutions and to increase industry awareness of our solutions.

      During 2005 we derived 55% of our total revenue from customers based in Asia compared to 64% in the year ended December 31, 2004 and 70% in the year ended December 31, 2003. Approximately 35% of our total revenue was derived from customers located in the United States in the year ended December 31, 2005 as compared to 25% and 22%, respectively, in the years ended December 31, 2004 and December 31, 2003. Additional discussion regarding the risks associated with international operation can be found under Item 1A, “Risk Factors”, on page 10.

      We strive to provide value in our initial engagement to solidify relationships at the executive level. Early in the solution implementation, our engineers seek to establish relationships in the organization and gain an understanding of our customers’ business issues. Our direct sales and solution implementation teams combine their efforts to deepen our customer relationships by expanding our penetration across the customer’s products, processes and technologies. This close working relationship with the customer has the added benefit of helping us identify new product areas and technologies in which we should next focus our research and development efforts.

      See Note 9 of our “Notes to Consolidated Financial Statements”, included under Part II, Item 8. “Financial Statements and Supplementary Data” for additional geographic information.

Research and Development

      Our research and development focuses on developing and introducing new proprietary technologies, software products and enhancements to our existing solutions. We use a rapid-prototyping paradigm in the context of the customer engagement to achieve these goals.

      We have made and expect to continue to make substantial investments in research and development. The complexity of our Design-to-Silicon-Yield technologies requires expertise in physical IC design and layout, transistor design and semiconductor physics, semiconductor process integration, numerical algorithms, statistics and software development. We believe that our team of engineers will continue to advance our market and technological leadership. We conduct in-house training for our engineers in the technical areas, as well as focusing on ways to enhance client service skills. At any given time, about one quarter of our research and development engineers are operating in the field, partnered with solution implementation engineers in a deliberate strategy to provide direct feedback between technology development and customer needs. Our research and development expenses excluding stock based compensation were approximately $22.1 million, $20.3 million and $18.4 million in 2005, 2004 and 2003, respectively.

Competition

      The semiconductor industry is highly competitive and characterized by rapidly changing design and process technologies, evolving standards, short product life cycles, and decreasing prices. While the market for process-design integration technologies and services is in its early stages, it is rapidly evolving and we expect competition to develop and continue to increase. We believe the solution to address IC companies needs requires a unified system of yield models, design analysis software, CV test chips, and yield management software. Currently, we are the only provider of comprehensive commercial solutions for integrating design and manufacturing processes. We face indirect competition from internal groups at IC companies that use an incomplete set of components that are not optimized to accelerate process-design integration. Some providers of yield management software, inspection equipment, or electronic design automation may seek to broaden their product offerings and compete with us.

      We face competition for some of the point applications of our solutions including some of those used by the internal groups at IC companies. Specifically there are several suppliers of yield management and/or prediction systems, such as KLA-Tencor, Knights Technology (a part of FEI Company), Ponte Solutions, Predictions Software, Syntricity, Spotfire, and Synopsys, Inc. In addition, Synopsys, Inc. now appears to offer

directly competing DFM capability, while other EDA suppliers provide alternative DFM solutions that may compete for the same budgetary funds.

      We believe the principal factors affecting competition in our market are:

      Although we believe that our solutions compete favorably with respect to these factors, our market is relatively new and is evolving rapidly. We may not be able to maintain our competitive position against current and potential competitors, especially those with significantly greater resources.

Employees

      As of December 31, 2005, we had 283 employees, including 110 on client service teams, 110 in research and development, 29 in sales and marketing and 34 in general and administrative functions. 199 of these employees are located in San Jose/ San Diego, California, 23 are located in Texas and other parts of the United States, 19 are located in Germany, 25 are located in Japan, 15 are located in Italy, and 2 employees are located in the Netherlands.

      None of our employees are represented by a labor union or are subject to a collective bargaining agreement. We believe our relationship with our employees is good.

Executive Officers

           The following table and notes set forth information about our current executive officers.

      John K. Kibarian, Ph.D., one of our founders, has served as President since November 1991 and has served as our Chief Executive Officer since July 2000. Mr. Kibarian has served as a director since December 1992. Mr. Kibarian received a B.S. in Electrical Engineering, a M.S. E.C.E. and a Ph.D. E.C.E. from Carnegie Mellon University.

      Keith A. Jones, has served as Chief Financial Officer and Vice President, Finance since January 2006. Mr. Jones served as Director of Finance and SEC Compliance from July 2003 to December 2005. Prior to joining PDF, from September 2001 to July 2003, he served as Assistant Controller for Interwoven, Inc., a provider of enterprise content management solutions. From May 2000 to July 2001, he served as Controller for eTime Capital, Inc., a financial software applications company. From July 1994 to April 2000, he served Deloitte & Touche LLP, a public accounting firm, in various positions and most recently as an Audit Manager. Mr. Jones received a B.S. in Business Administration from California State University, Fresno and is a Certified Public Accountant.

      David A. Joseph has served as Chief Strategy Officer since April 2003. Mr. Joseph served as Executive Vice President Sales, Marketing, and Business Development from August 2001 through March 2003. He served as Vice President, Products and Methods from July 1999 through August 2001 and as Vice President, Business Development from November 1998 through June 1999. Prior to joining PDF, from February 1978 to October 1998, Mr. Joseph served KLA-Tencor, a semiconductor manufacturing company, in various positions, including as Japan Business Manager, Vice President Customer Satisfaction and General Manager of Yield Analysis Software. Mr. Joseph received a B.S. in Mathematical Science from Stanford University.

      Rebecca Baybrook has served as Vice President, Human Resources since May 2002. Prior to joining PDF, from September 2001 to April 2002, Ms. Baybrook served as Sr. Director, Human Resources for Vitria Technologies, an integrated software company. From October 1999 to July 2001 she served as Director, Human Resources for 3Com, a telecommunications company. From January 1986 to September 1999, Ms. Baybrook served as Assistant Vice President of Human Resources for Knight Ridder, Inc., a publishing company. Ms. Baybrook received B.A. degree from Westmont College and a Ph.D. in Organizational Psychology from University of South Florida.

      Cees Hartgring Ph.D., has served as Vice President and General Manager, Manufacturing Process Solutions since January 2004. Mr. Hartgring served as Vice President, Worldwide Sales and Strategic Business Development from April 2003 through December 2003. He served as Vice President of Sales from September 2002 through March 2003. Prior to joining PDF, from May 2000 to August 2001, Mr. Hartgring served as President and Chief Executive Officer of Trimedia Technologies, a Philips Semiconductor spinout. From August 1990 to April 2000, he held various executive positions at Philips Semiconductor, most recently as Vice President and General Manager of the Trimedia business unit. Mr. Hartgring has an undergraduate degree from the Technical University Delft and a M.S.E.E. and a Ph.D. in Electrical Engineering and Computer Science from the University of California at Berkeley.

      Andre Hawit has served as Vice President and General Manager, Yield Manufacturing Solutions since January 2006. Mr. Hawit served as Vice President, Software Development from September 2003 through December 2005. Prior to joining PDF, Mr. Hawit was the founder of IDS Software Systems Inc., a yield management systems software and solutions company. From October 1991 through August 2003, he held various positions within IDS including President and Chief Executive Officer, and most recently Chief Technology Officer. Mr. Hawit received a B.S. in Electronics and Computer Engineering from San Francisco State University and an M.B.A. from National University School of Business.

      James Jensen has served as Vice President, Engineering Services for Manufacturing Process Solutions since January 2006. Mr. Jensen served as Co-Vice President, Client Services from November 2003 through December 2005 and as Director of Business Development, Integrated Yield Ramp Solutions, from March 2002 through October 2003. Prior to joining PDF, from July 1996 through February 2002, he served as General Manager of a semiconductor fabrication facility of Texas Instruments, a semiconductor products company. From November 1989 through June 1996, Mr. Jensen served as Fabrication Operations Director for Silicon Systems Inc., a semiconductor products company. Mr. Jensen received a B.S. in Physics from the University of Utah and a M.S. in Management from Purdue University.

      Kevin MacLean, has served as Vice President, Marketing and Development for Manufacturing Process Solutions since January 2006. Mr. MacLean served as Vice President and General Manager of Design For Manufacturability (DFM) Solutions from June 2004 through December 2005. Prior to joining PDF, from June 2003 to October 2003, Mr. MacLean served as Senior Vice President and General Manager of DFM Solutions at Cadence Design Systems, Inc., an electronic design automation software company. From January 2000 to January 2002, he served as Sr. Vice President and Chair of the Technology Council for Numerical Technologies, a provider of subwavelength lithography-enabling technology. Mr. MacLean was a cofounder of Transcriptions Enterprises. From June 1986 to January 2002, he held various positions at Transcription Enterprises most recently as General Manager, after the merger with Numerical Technologies in January 2000. Mr. MacLean received a B.S. in Engineering from Cornell University.

      Zia Malik has served as Vice President, Sales since December 2003. Prior to joining PDF, from September 2000 through November 2003, Mr. Malik served as Vice President of Operations and Customer Marketing of Ishoni Networks, a maker of broadband networking processors. From February 1997 through September 2000, he served as a Senior Director for the Foundry and Contracts Manufacturing Group of National Semiconductor Corporation, an integrated circuit manufacturer. From June 1987 through February 1997, he held various executive positions at California Micro Devices Corporation, a maker of semiconductors, most recently as Vice President of Business Development. Mr. Malik received a B.S. and M.S. in Chemistry from the University of Karachi in Pakistan and an MBA from the University of Phoenix.

      P. Steven Melman has served as Vice President, Investor Relations and Strategic Initiatives since January 1, 2006. Mr. Melman served as Chief Financial Officer and Vice President, Finance and Administration from July 1998 to December 2005. Prior to joining PDF, from April 1997 to June 1998, he served as Vice President Finance and Administration with Animation Science Corporation, an animation company. From April 1995 to April 1997, he served as Vice President, Finance and Chief Financial Officer with Business Resource Group, a facilities management and commercial furnishings company. Mr. Melman received a B.S. in Business Administration from Boston University. Mr. Melman is a Certified Public Accountant.

      Kimon Michaels, Ph.D., one of our founders, has served as Vice President, Field Operations for Manufacturing Process Solutions since January 2006, and has been a Director since November 1995. From March 1993 through December 2005, he served in various vice presidential capacities. He also served as Chief Financial Officer from November 1995 to July 1998. Mr. Michaels received a B.S. in Electrical Engineering, a M.S. E.C.E. and a Ph.D. E.C.E. from Carnegie Mellon University.

Available Information

      Our Internet website address is www.PDF.com. You may obtain, free of charge on our Internet website, copies of our annual report on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K, and amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended, as soon as reasonably practicable after we electronically file such material with, or furnish it to, the Securities and Exchange Commission. The information we post is intended for reference purposes only; none of the information posted on our website is part of this report or incorporated by reference herein.

      If semiconductor designers and manufacturers do not continue to adopt our Design-to-Silicon-Yield solutions, our revenue could decline. To date, we have worked with a limited number of semiconductor companies on a limited number of IC products and processes. To be successful, we will need to continue to enter into agreements covering a larger number of IC products and processes with existing customers and new customers. Our existing customers are primarily large integrated device manufacturers, or IDMs. We target as new customers additional IDMs, fabless semiconductor companies, and foundries, as well as system

manufacturers. Factors that may limit adoption of our Design-to-Silicon-Yield solutions by semiconductor companies include:

      Historically, we have had a small number of large customers for our core Design-to-Silicon-Yield solutions and we expect this to continue in the near term. In the year ended December 31, 2005, four customers accounted for 49% of our total net revenue, with Texas Instruments representing 15%, IBM representing 13%, Matsushita representing 11% and Toshiba representing 10%, respectively. In the year ended December 31, 2004, four customers accounted for 52% of our total net revenue, with Toshiba representing 17%, Sony representing 13%, Matsushita representing 12% and Texas Instruments representing 10%, respectively. The loss of any of these customers or a decrease in the sales volumes of their products could significantly reduce our total revenue below expectations. In particular, such a loss could cause significant fluctuations in results of operations because our expenses are fixed in the short term and it takes us a long time to replace customers.

      We will need to continue to grow in all areas of operation and successfully integrate and support our existing and new employees into our operations, or we may be unable to implement our business strategy in the time frame we anticipate, if at all. We have in the past, and may in the future, experience interruptions in our information systems on which our global operations depend. Further, physical damage to, failure of, or digital damage (such as significant viruses or worms) to, our information systems could disrupt and delay time-sensitive services or computing operations that we perform for our customers, which could negatively impact our business results and reputation. We may need to switch to a new accounting system in the near future, which could disrupt our business operations and distract management. In addition, we will need to expand our intranet to support new data centers to enhance our research and development efforts. Our intranet is expensive to expand and must be highly secure due to the sensitive nature of our customers’ information that we transmit. Building and managing the support necessary for our growth places significant demands on our management and resources. These demands may divert these resources from the continued growth of our business and implementation of our business strategy. Further, we must adequately train our new personnel, especially our client service and technical support personnel, to effectively and accurately, respond to and support our customers. If we fail to do this, it could lead to dissatisfaction among our customers, which could slow our growth.

      Our success depends largely on the proprietary nature of our technologies. We currently rely primarily on copyright, trademark, and trade secret protection. Whether or not patents are granted to us, litigation may be necessary to enforce our intellectual property rights or to determine the validity and scope of the proprietary rights of others. As a result of any such litigation, we could lose our proprietary rights and incur substantial unexpected operating costs. Litigation could also divert our resources, including our managerial and engineering resources. In the future, we intend to rely primarily on a combination of patents, copyrights, trademarks, and trade secrets to protect our proprietary rights and prevent competitors from using our proprietary technologies in their products. These laws and procedures provide only limited protection. Our pending patent applications may not result in issued patents, and even if issued, they may not be sufficiently broad to protect our proprietary technologies. Also, patent protection in foreign countries may be limited or unavailable where we need such protection.

      Competition in our market may intensify in the future, which could slow our ability to grow or execute our strategy. Our current and potential customers may choose to develop their own solutions internally, particularly if we are slow in deploying our solutions. Many of these companies have the financial and technical capability to develop their own solutions. Also, competitors could establish non-domestic operations with a lower cost structure than our engineering organization, which, unless we also establish lower cost non-domestic operations, would give any such competitor’s products a competitive advantage over our solutions. There may be other providers of commercial solutions for systematic IC yield and performance enhancement of which we are not aware. We currently face indirect competition from the internal groups at IC companies and some direct competition from providers of yield management or prediction software such as Knights Technology (a part of FEI Company), Ponte Solutions, Predictions Software, Syntricity, Spotfire and Synopsys (through their acquisition of HPL Technologies). Some providers of yield management software or inspection equipment may seek to broaden their product offerings and compete with us. For example, KLA-Tencor has announced adding the use of test structures to one of their inspection product lines. In addition, we believe that the demand for solutions that address the need for better integration between the silicon design and manufacturing processes may encourage direct competitors to enter into our market. For example, large integrated organizations, such as IDMs, electronic design automation software providers, IC design service companies or semiconductor equipment vendors, may decide to spin-off a business unit that competes with us. Other potential competitors include fabrication facilities that may decide to offer solutions competitive with ours as part of their value proposition to their customers. In addition, Synopsys, Inc. now appears to offer directly competing DFM capability, while other EDA suppliers provide alternative DFM solutions that may compete for the same budgetary funds. If these potential competitors are able to attract industry partners or customers faster than we can or change the pricing environment, we may not be able to grow and execute our strategy as quickly or at all. In addition, customer preferences may shift away from our solutions as a result of the increase in competition.

      We derive a majority of our revenue from international sales, principally from customers based in Asia. Revenue generated from customers in Asia accounted for 55% of total revenue in the year ended December 31, 2005. During the year ended December 31, 2004 revenue generated from customers in Asia was 64% of total revenue. We expect that a significant portion of our total future revenue will continue to be derived from companies based in Asia. In addition, we have expanded our non-U.S. operations recently and plan to continue such expansion by establishing overseas subsidiaries, offices, or contractor relationships in

locations, and when, deemed appropriate by our management. The success of our business is subject to risks inherent in doing business internationally. These risks include:

      In Japan, in particular, we face the following additional risks:

      Historically, our quarterly operating results have fluctuated. Our future quarterly operating results will likely fluctuate from time to time and may not meet the expectations of securities analysts and investors in some future period. The price of our common stock could decline due to such fluctuations. The following factors may cause significant fluctuations in our future quarterly operating results:

      Our gain share revenue for a particular product is largely determined by the volume of that product that our customer is able to sell to its customers, which is outside of our control. We have limited ability to predict the success or failure of our customers’ IC products. Further, our customers may implement changes to their manufacturing processes during the gain share period, which could negatively affect yield results, which is beyond our control. We may commit a significant amount of time and resources to a customer who is ultimately unable to sell as many units as we had anticipated when contracting with them or who makes unplanned changes to their processes. Since we currently work on a small number of large projects, any product that does not achieve commercial viability or a significant increase in yield could significantly reduce our revenue and results of operations below expectations. In addition, if we work with two directly competitive products, volume in one may offset volume, and any of our related gain share, in the other product. Further, decreased demand for semiconductor products decreases the volume of products our customers are able to sell, which may adversely affect our gain share revenue.

      We can only recognize gain share revenue once we have reached agreement with our customers on their level of yield performance improvements. Because measuring the amount of yield improvement is inherently complicated and dependent on our customers’ internal information systems, there may be uncertainty as to some components of measurement. This could result in our recognition of less revenue than expected. In addition, any delay in measuring gain share could cause all of the associated revenue to be delayed until the next quarter. Since we currently have only a few large customers and we are relying on gain share as a significant component of our total revenue, any delay could significantly harm our quarterly results.

      Our long-term success is largely dependent upon our ability to structure our future customer contracts to include a larger gain share component relative to the fixed fee component. If we are successful in increasing the gain share component of our customer contracts, we will experience an adverse impact on our operating results in the short term as we reduce the fixed fee component, which we typically recognize earlier than gain share fees. Due to acquisitions and expanded business strategies, the mix of elements in some of our contracts has changed recently and the relative importance of the software component in some of our contracts has increased. We have experienced, and may in the future experience, delays in the expected recognition of revenue associated with generally accepted accounting principles regarding the timing of revenue recognition in multi-element software arrangements, including the effect of acceptance criteria. If we fail to meet contractual acceptance criteria on time or at all, the total revenue we receive under a contract could be delayed or decline. In addition, by increasing the gain share or the software component, we may increase the variability or timing of recognition of our revenue, and therefore increase the risk that our total future revenue will be lower than expected and fluctuate significantly from period to period.

      Because our gain share business model is unique and our Design-to-Silicon-Yield solutions are unfamiliar, our sales cycle is lengthy and requires a significant amount of our senior management’s time and effort. Furthermore, we need to target those individuals within a customer’s organization who have overall responsibility for the profitability of an IC. These individuals tend to be senior management or executive

officers. We may face difficulty identifying and establishing contact with such individuals. Even after initial acceptance, due to the complexity of structuring the gain share component, the negotiation and documentation processes can be lengthy. It can take nine months or more to reach a signed contract with a customer. Unexpected delays in our sales cycle could cause our revenue to fall short of expectations.

      While we were profitable on a GAAP basis in our six most recent quarters, we have experienced losses in the past. We may not maintain profitability if our revenue increases more slowly than we expect or not at all. In addition, virtually all of our operating expenses are fixed in the short term, so any shortfall in anticipated revenue in a given period could significantly reduce our operating results below expectations. Our accumulated deficit was $13.5 million as of December 31, 2005. We expect to continue to incur significant expenses in connection with:

      As a result, we will need to significantly increase revenue to maintain profitability on a quarterly or annual basis. Any of these factors could cause our stock price to decline.

      Our revenue is highly dependent upon the overall condition of the semiconductor industry, especially in light of our gain share revenue component. The semiconductor industry is highly cyclical and subject to rapid technological change and has been subject to significant economic downturns at various times, characterized by diminished product demand, accelerated erosion of average selling prices, and production overcapacity. The semiconductor industry also periodically experiences increased demand and production capacity constraints. As a result, we may experience significant fluctuations in operating results due to general semiconductor industry conditions and overall economic conditions.

      We will need to continue to hire highly talented executives, engineers, and research and development personnel to support our planned growth. We have experienced, and we expect to continue to experience, delays and limitations in hiring and retaining highly skilled individuals with appropriate qualifications. We intend to continue to hire foreign nationals, particularly as we expand our operations internationally. We have had, and expect to continue to have, difficulty in obtaining visas permitting entry into the United States for several of our key personnel, which disrupts our ability to strategically locate our personnel. If we lose the services of any of our key executives or a significant number of our engineers, it could disrupt our ability to implement our business strategy. Competition for executives and qualified engineers can be intense, especially in Silicon Valley where we are principally based.

      We must continually devote significant engineering resources to enable us to keep up with the rapidly evolving technologies and equipment used in the semiconductor design and manufacturing processes. These innovations are inherently complex and require long development cycles. Not only do we need the technical expertise to implement the changes necessary to keep our technologies current, we also rely heavily on the judgment of our advisors and management to anticipate future market trends. Our customers expect us to stay

ahead of the technology curve and expect that our products, technologies, services, and integrated solutions will support any new design or manufacturing processes or materials as soon as they are deployed. If we are not able to timely predict industry changes, or if we are unable to modify our products, technologies, services, and integrated solutions on a timely basis, our existing solutions will be rendered obsolete and we may lose customers. If we do not keep pace with technology, our existing and potential customers may choose to develop their own solutions internally as an alternative to ours and we could lose market share, which could adversely affect our operating results.

      In order to establish and maintain strategic relationships with industry leaders at each stage of the IC design and manufacturing processes, we may need to expend significant resources and will need to commit a significant amount of management’s time and attention, with no guarantee of success. If we are unable to enter into strategic relationships with these companies, we will not be as effective at modeling existing technologies or at keeping ahead of the technology curve as new technologies are introduced. In the past, the absence of an established working relationship with key companies in the industry has meant that we have had to exclude the effect of their component parts from our modeling analysis, which reduces the overall effectiveness of our analysis and limits our ability to improve yield. We may be unable to establish key industry strategic relationships if any of the following occur:

      Our solution implementations require a team of engineers to collaborate with our customers to address complex yield loss issues by using our software and other technologies. We must estimate the amount of time needed to complete an existing solution implementation in order to estimate when the engineers will be able to commence a new solution implementation. In addition, our accounting for solution implementation contracts, which generate fixed fees, sometimes require adjustments to profit and loss based on revised estimates during the performance of the contract. These adjustments may have a material effect on our results of operations in the period in which they are made. The estimates giving rise to these risks, which are inherent in fixed-price contracts, include the forecasting of costs and schedules, and contract revenues related to contract performance.

      Our future success will depend to a significant extent on the continued services of our key executives, including John Kibarian, our President and Chief Executive Officer, and David Joseph, our Chief Strategy Officer. If we lose the services of any of our key executives, it could slow execution of our business plan, hinder our product development processes and impair our sales efforts. Searching for replacements could divert other senior management’s time and increase our operating expenses. In addition, our industry partners and customers could become concerned about our future operations, which could injure our reputation. We do not have long-term employment agreements with our executives and we do not maintain any key person life insurance policies on their lives.

      Our customers consider their product yield information and other confidential information, which we must gather in the course of our engagement with the customer, to be extremely competitively sensitive. If we inadvertently disclosed or were required to disclose this information, we would likely lose existing and potential customers and could be subject to costly litigation. In addition, to avoid potential disclosure of confidential information to competitors, some of our customers may, in the future, ask us not to work with key competitive products.

      Significant litigation regarding intellectual property rights exists in the semiconductor industry. It is possible that a third party may claim that our technologies infringe their intellectual property rights or misappropriate their trade secrets. Any claim, even if without merit, could be time consuming to defend, result in costly litigation, or require us to enter into royalty or licensing agreements, which may not be available to us on acceptable terms, or at all. A successful claim of infringement against us in connection with the use of our technologies could adversely affect our business.

      If the software, hardware, or proprietary technologies we provide to a customer contain defects that increase our customer’s cost of goods sold and time to market, these defects could significantly decrease the market acceptance of our solutions. Further, the cost of support resources required to remedy any defects in our technologies, hardware, or software tools could exceed our expectations. Any actual or perceived defects with our software, hardware, or proprietary technologies may also hinder our ability to attract or retain industry partners or customers, leading to a decrease in our revenue. These defects are frequently found during the period following introduction of new software, hardware, or proprietary technologies or enhancements to existing software, hardware, or proprietary technologies. Our software, hardware, and proprietary technologies may contain errors not discovered until after customer implementation of the silicon design and manufacturing process recommended by us. If our software, hardware, or proprietary technologies contain errors or defects, it could require us to expend significant resources to alleviate these problems, which could reduce margins and result in the diversion of technical and other resources from our other development efforts.

      Pursuant to Section 404 of the Sarbanes-Oxley Act, we are required to furnish a report on our management’s assessment of the design and effectiveness of our system of internal control over financial reporting as part of our Annual Report on Form 10-K. Our auditors are also required to attest to, and report on, our management’s assessment. In order to issue their report, our management is required to document both the design of our system of internal controls and our testing processes that support our management’s evaluation and conclusion. While our management and independent auditors have been able to conclude that our internal control over financial reporting has been effective in each of the last two years, during the course of future testing, we may identify deficiencies, including those arising from turnover of qualified personnel or arising as a result of acquisitions, which we may not be able to remediate in time to meet the continuing reporting deadlines imposed by Section 404 and the costs of which may harm our results of operations. In addition, if we fail to maintain the adequacy of our internal controls, as such standards are modified, supplemented or amended from time to time, we may not be able to ensure that our management can conclude on an ongoing basis that we have effective internal controls. We also may not be able to retain independent auditors with sufficient resources to attest to and report on our internal controls in a timely manner. Moreover, our auditors may not agree with our management’s future assessments and may send us a deficiency notice that we are unable to remediate on a timely basis. If we are unable to assert as of December 31, 2006 and beyond, that we maintain effective internal controls, our investors could lose

confidence in the accuracy and completeness of our financial reports that in turn could cause our stock price to decline.

      Technology companies have, in general, and our company has, in particular, a history of depending upon and using broad based employee stock option programs to hire, incentivize and retain employees in a competitive marketplace. In December 2004, the Financial Accounting Standards Board (“FASB”) released Statement of Financial Accounting Standard No. 123(R), Share-Based Payments (“SFAS No. 123(R)”), which will require all companies to measure compensation costs for all share-based payments, including employee stock options, at fair value. The provisions of SFAS No. 123(R) are effective for us beginning January 1, 2006. While we are currently still evaluating the actual effect that the adoption of SFAS No. 123(R) will have on our financial position and results of operations, we believe that our adoption of SFAS No. 123(R) will have a significant negative impact on our financial position and results of operations. In addition, we believe that the adoption of SFAS No. 123(R) may impact our ability to utilize broad based employee stock option plans to hire, incentivize and retain employees and could result in a competitive disadvantage to us in the employee marketplace.

      Future political or related events similar or comparable to the September 11, 2001 terrorist attacks, or significant military conflicts, or long-term reactions of governments and society to such events, may cause significant delays or reductions in technology purchases or limit our ability to travel to certain parts of the world. In addition, such events have had and may continue to have negative effects on financial markets, including significant price and volume fluctuations in securities markets. If such events continue or escalate, our business and results of operations could be harmed and the market price of our common stock could decline.

      To expand our proprietary technologies, we may acquire or make investments in complementary businesses, technologies, or products if appropriate opportunities arise. We may be unable to identify suitable acquisition or investment candidates at reasonable prices or on reasonable terms, or consummate future acquisitions or investments, each of which could slow our growth strategy. We may have difficulty integrating the acquired products, personnel or technologies of any acquisitions we might make. These difficulties could disrupt our ongoing business, distract our management and employees and increase our expenses.

      We currently anticipate that our available cash resources will be sufficient to meet our presently anticipated working capital and capital expenditure requirements for at least the next 12 months. However, unanticipated efforts to support more rapid expansion, develop or enhance Design-to-Silicon-Yield solutions, respond to competitive pressures or acquire complementary businesses or technologies could impact our future capital requirements and the adequacy of our available funds. In such event, we may need to raise additional funds through public or private financings, strategic relationships or other arrangements. We may not be able to raise any necessary funds on terms favorable to us, or at all.

      None.

      Our principal executive offices are located in San Jose, California where we lease approximately 40,600 square feet under two leases, one for 39,100 square feet that expires in January 2008 and the other for 1,500 square feet on a month to month basis. We lease 11,200 square feet of office and laboratory space in San Diego, California under a lease that expires in March 2008. We lease 5,100 square feet in Dallas, Texas under a lease that expires in May 2008. We lease and sublease 3,000 square feet in Foster City, California under a lease that expires in September 2007. We lease 275 square feet in Amherst, New Hampshire under a lease that expires in August 2006. In addition, we lease 11,000 square feet in Munich, Germany, 2,600 square feet in Tokyo, Japan and 3,500 square feet in Desenzano, Italy under leases that expire in January 2012, April 2006, and December 2008, respectively. We believe our existing facilities and those in negotiation are adequate to meet our current needs and are being utilized in line with our past experience.

      We are not currently party to any material legal proceedings.

      None.

PART II

      Our common stock has traded on the Nasdaq National Market under the symbol “PDFS” since our initial public offering on July 26, 2001. As of February 28, 2006 we had approximately 225 stockholders of record and the closing price of our common stock was $16.89 per share as reported by the Nasdaq National Market. The number of stockholders of record does not include individuals whose stock is in nominee or “street name” accounts through brokers.

      The following table sets forth for the periods indicated the high and low closing sale prices for our common stock as reported by the Nasdaq National Market:

      The information under the heading “Equity Compensation Plan Information” in our definitive Proxy Statement (our “Proxy Statement”) to be filed with the Security and Exchange Commission (SEC) in connection with our 2006 Annual Meeting of Stockholders is incorporated into Item 5 of this report by reference.

      The table below sets forth the information with respect to purchases made by or on behalf of the Company or any “affiliated purchaser” (as the term is defined in Rule 10b-18(a)(3) under the Securities Exchange Act of 1934) of our common stock during the fourth quarter of the year ended December 31, 2005:

ISSUER PURCHASES OF EQUITY SECURITIES

Dividend Policy

      No cash dividends were declared or paid in 2005 or 2004. We currently intend to retain all available funds to finance future internal growth and product development and do not anticipate paying any cash dividends on our common stock for the foreseeable future.

      The following selected financial information has been derived from the audited consolidated financial statements. The information set forth below is not necessarily indicative of results of future operations and should be read in conjunction with Item 7. “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and the consolidated financial statements and notes to those statements included therein and in Part II of this Form 10-K.

Forward-Looking Statements

      You should read the following discussion in conjunction with our consolidated financial statements and notes set forth under Item 8. “Financial Statements and Supplementary Data” and “Risk Factors” included in Item 1A. The results described below are not necessarily indicative of the results to be expected in any future period. Certain statements in this discussion and analysis, including statements regarding our strategy, financial performance and revenue sources, are forward-looking statements based on current expectations and entail various risks and uncertainties that could cause actual results to differ materially from those expressed in the forward-looking statements, including those described in Item 1A.“Risk Factors” and elsewhere in this Form 10-K.

Overview

      Our technologies and services enable semiconductor companies to improve the yield and performance of integrated circuits, or ICs, by integrating the design and manufacturing processes. We believe that our solutions improve a semiconductor company’s time-to-market, yield and ultimately product profitability. Our solutions combine proprietary manufacturing process simulation software, yield and performance modeling software, design-for-manufacturability software, test chips, a proprietary electrical wafer test system, yield and performance enhancement methodologies, yield management systems, and professional services. We analyze yield loss mechanisms to identify, quantify and correct the issues that cause yield loss, as an integral part of the IC design process. This drives IC design and manufacturing improvements that enable our customers to have higher initial yields and achieve and exceed targeted IC yield and performance throughout product life cycles. Our solution is designed to increase the initial yield when a design first enters a manufacturing line, to increase the rate at which that yield improves, and to allow subsequent product designs to be added to manufacturing lines more quickly and easily.

      The result of implementing our solutions is the creation of value that can be measured based on improvements to our customers’ actual yield. We align our financial interests with the yield and performance improvements realized by our customers, and receive revenue based on this value. To date, we have sold our technologies and services to semiconductor companies including leading integrated device manufacturers, fabless semiconductor companies and foundries.

      From our incorporation in 1992 through late 1995, we were primarily focused on research and development of our proprietary manufacturing process simulation and yield and performance modeling software. From late 1995 through late 1998, we continued to refine and sell our software, while expanding our offering to include yield and performance improvement consulting services. In late 1998, we began to sell our software and consulting services, together with our newly developed proprietary technologies, as Design-to-Silicon-Yield solutions, reflecting our current business model. In April 2000, we expanded our research and development team and gained additional technology by acquiring AISS, now operating as PDF Solutions, GmbH, which continues to develop software and provide development services to the semiconductor industry. In July 2001, we completed the initial public offering of our common stock. In 2003, we further enhanced our product and service offerings through the acquisitions of IDS and WaferYield.

      Demand for consumer electronics continues to drive technological innovation as the need for products which have greater performance, lower power consumption, reduced costs and smaller size continues to grow with each new product generation. To meet this demand, IC manufacturers and designers are constantly challenged to improve the overall performance of ICs by designing and manufacturing ICs with more embedded applications to create greater functionality. As a result, in 2004 and through 2005 more and more companies have expanded or advanced their design and manufacturing processes to develop and produce deep submicron ICs containing component sizes measured at 130 nanometers and below. As this trend continues, companies will continually be challenged to improve process capabilities to optimally produce ICs with minimal systematic and yield loss, which is driven by the lack of compatibility between the design and its respective manufacturing process. We believe as volume production of deep submicron ICs continues to grow, the difficulties of integrating IC designs with their respective processes will create a greater need for products and services that address the performance yield loss issues the semiconductor industry is facing today and will face in the future.

      During 2005 we continued to see greater adoption of our products and services through the expansion of our customer base both domestically and internationally. Financial highlights for the year ended December 31, 2005 were as follows:

      On May 31, 2003, we completed our acquisition of WaferYield, which primarily included WaferYield’s proprietary shot map WAMA^® technology and related business. The WAMA^® product offering was designed to optimize semiconductor wafer shot maps to help semiconductor companies achieve greater yield and net die per wafer, higher stepper throughput and reduced probe test cost. The Company has fully integrated the WAMA^® technology into optional modules for its dataPOWER software product, which modules it licenses under the names dp-shotMAP and dp-probeMAP. We believe that the acquisition added to our product offering and our capabilities in enabling semiconductor companies to improve yield and performance of ICs. The aggregate purchase price was $4.1 million, which included cash payments of $2.6 million and the recognition of $1.5 million in other liabilities associated with future payments that were contingent upon the attainment of certain revenue performance objectives. Such revenue performance objectives could have resulted in future payments of up to $5.0 million. During the year ended December 31, 2004, we agreed to pay $1.0 million to settle such future contingent payments. As a result of this payment, the remaining $4.0 million payable under the original agreement is no longer payable. Upon final settlement of this liability, we reduced the purchase price by $500,000 reflecting the difference between the incentive amount paid and the related liability recorded in connection with the acquisition.

      On September 24, 2003, we completed our acquisition of all the outstanding stock of IDS. IDS developed and licensed yield management software applications and provided services to enable customers to efficiently gather, retrieve and analyze manufacturing data, identifying areas for yield improvement. We believe that our acquisition of IDS provides our customers with greater capabilities for managing product yield improvement through the use of the acquired technology and services. The aggregate purchase price was $51.0 million which included the payment in cash of $23.0 million, the issuance of 2.0 million shares of our common stock valued at $25.0 million, the assumption of stock options valued at $1.7 million and acquisition costs of $1.3 million. In connection with the acquisition, $1.0 million in cash and 400,000 shares of common stock were held in escrow as security against certain financial contingencies. In October 2004, we released all cash held in escrow to the shareholders of IDS. Fifty percent of the shares held in escrow, less amounts deducted to satisfy contingencies, were released upon the 12-month anniversary of the acquisition. The remaining shares held in escrow were released upon the 24-month anniversary of the acquisition. In connection with the acquisition, we recorded $39.2 million in goodwill, net of subsequent adjustments related to certain accruals and tax liabilities recognized in the acquisition. Goodwill reflects the excess of the purchase price paid over the identifiable assets assumed in the acquisition.

Critical Accounting Policies

      Financial Reporting Release No. 60 requires all companies to include a discussion of critical accounting policies or methods used in the preparation of financial statements. Note 1 of the notes to the consolidated financial statements includes a summary of the significant accounting policies and methods used in the preparation of our consolidated financial statements. The following is a brief discussion of the more significant accounting policies and methods that we use.

      Our discussion and analysis of our financial condition and results of operations are based on our consolidated financial statements, which have been prepared in conformity with accounting principles generally accepted in the United States of America. Our preparation of these consolidated financial

statements requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of the financial statements and the reported amounts of revenues and expenses during the reporting periods. We based our estimates on historical experience and on various other assumptions that we believe to be reasonable under the circumstances. The most significant estimates and assumptions relate to revenue recognition, software development costs, recoverability of goodwill and acquired intangible assets, estimated useful lives of acquired intangibles and the realization of deferred tax assets. Actual amounts may differ from such estimates under different assumptions or conditions.

      We derive revenue from two sources: Design-to-Silicon-Yield solutions and gain share. We recognize revenue in accordance with the provisions of American Institute of Certified Public Accountants’ Statement of Position (“SOP”) No. 81-1, Accounting for Performance of Construction-Type and Certain Production-Type Contracts and SOP No. 97-2, Software Revenue Recognition, as amended.

      Design-to-Silicon-Yield Solutions — Design-to-Silicon-Yield solutions revenue is derived from integrated solutions and software licenses. Revenue recognition for each element of Design-to-Silicon-Yield solutions is as follows:

      Gain Share — Gain share revenue represents profit sharing and performance incentives earned based upon our customers reaching certain defined operational levels. Upon achieving such operational levels, we receive either a fixed fee and/or variable fee based on the units sold by the customer. Due to the uncertainties surrounding attainment of such operational levels, we recognize gain share revenue (to the extent of completion of the related solution implementation contract) upon receipt of performance reports or other related information from our customers supporting the determination of amounts and probability of collection. Gain share revenue is dependent on many factors which are outside our control, including among others, continued production of the related ICs by our customers, sustained yield improvements by our customers and our ability to enter into new Design-to-Silicon-Yield solutions contracts containing gain share provisions.

      Costs for the development of new software products and substantial enhancements to existing software products are expensed as incurred until technological feasibility has been established, at which time any additional costs would be capitalized in accordance with Statement of Financial Accounting Standards (“SFAS”) No. 86, Computer Software to be Sold, Leased or Otherwise Marketed. Because we believe our current process for developing software is essentially completed concurrently with the establishment of technological feasibility, no costs have been capitalized to date.

      As of December 31, 2005, we had $49.7 million of goodwill and intangible assets. In assessing the recoverability of our goodwill and intangible assets, we must make assumptions regarding estimated future cash flows and other factors. If these estimates or their related assumptions change in the future, we may be required to record impairment charges for these assets, which would have a material adverse effect on our operating results. We evaluate goodwill for impairment pursuant to the provisions of SFAS No. 142, Goodwill and Other Intangible Assets. We have selected December 31 as the date upon which to perform our annual testing for impairment. As of December 31, 2005, we completed our annual testing requirements and determined that the carrying value of goodwill had not been impaired.

      We are currently amortizing our acquired intangible assets over estimated useful lives of 4 years, which is based on the estimated period of benefit to be delivered from such assets. However, a decrease in the estimated useful lives of such assets would cause additional amortization expense or an impairment of such asset in future periods.

      Realization of deferred tax assets is dependent on our ability to generate future taxable income and utilize tax planning strategies. We have recorded a deferred tax asset in the amount that is more likely than not to be realized based on current estimations and assumptions. We evaluate the valuation allowance on a quarterly basis. Any resulting changes to the valuation allowance will result in an adjustment to income in the period the determination is made.

Results of Operations

      The following table sets forth, for the years indicated, the percentage of total revenue represented by the line items reflected in our consolidated statements of operations:

      Design-to-Silicon-Yield Solutions. Design-to-Silicon-Yield solutions revenue is derived from integrated solutions (including solution implementations, software support and maintenance and training) and software licenses, provided during our customer yield improvement engagements and solution product sales.

      Gain Share. Gain share revenue represents profit sharing and performance incentives earned based upon our customer reaching certain defined operational levels. Gain share revenue increased approximately $4.1 million for the year ended December 31, 2005 compared to the year ended December 31, 2004. The increase in gain share revenue was primarily due to a greater number of engagements contributing to gain share at newer technology nodes, as well as a greater number of wafer starts at our customers’ sites. Our gain share revenue may continue to fluctuate from period to period. Gain share revenue is dependent on many factors that are outside our control, including among others, continued production of ICs by our customers, sustained yield improvements by our customers and our ability to enter into new Design-to-Silicon-Yield solutions contracts containing gain share provisions.

      Direct Costs of Design-to-Silicon-Yield Solutions. Direct costs of Design-to-Silicon-Yield solutions consists of costs incurred to provide and support our integrated solutions and costs recognized in connection with licensing our software.

      Amortization of Acquired Core Technology. Amortization of acquired core technology consists of the amortization of intangibles acquired as a result of certain business combinations. The decrease in the amortization of acquired core technology expense of $145,000 for the year ended December 31, 2005 compared to the year ended December 31, 2004 was primarily attributable to certain acquired core technology being fully amortized in prior periods. We anticipate amortization of acquired core technology to be $5.1 million in 2006 and $3.2 million in 2007.

      Research and Development. Research and development expenses consist primarily of personnel-related costs to support product development activities, including compensation and benefits, outside development services, travel and facilities cost allocations. The increase in research and development expenses of $1.8 million for the year ended December 31, 2005 compared to the year ended December 31, 2004 was primarily due to increased personnel-related expenses, a result of our growth in headcount, and to increased outside development expenses, a result of engaging additional consultants. We anticipate that we will continue to commit considerable resources to research and development in the future and that these expenses may increase in absolute dollars.

      Selling, General and Administrative. Selling, general and administrative expenses consist primarily of compensation and benefits for sales, marketing and general and administrative personnel in addition to outside sales commissions, legal and accounting services, marketing communications, travel and facilities cost allocations. The increase in selling, general and administrative expenses of $931,000 for the year ended December 31, 2005 compared to the year ended December 31, 2004 was primarily due to increases in personnel-related expenses, legal and accounting services, a reduction in our allowance for doubtful accounts in the prior year, partially offset by a reduction in outside sales commissions.

      Stock-Based Compensation Amortization. The Company recognizes deferred stock-based compensation expense under the provisions of APB No. 25 Accounting for Stock Issued to Employees, using the graded vesting method for amortization purposes. The decrease in stock-based compensation amortization of $636,000 for the year ended December 31, 2005 compared to the year ended December 31, 2004 was primarily due to the effects of the graded vesting method of amortization which results in higher amortization expense during the initial periods following the respective option grants and due to the recognition of $45,000 associated with the grant of 10,000 fully-vested stock options to a non-employee during the year ended December 31, 2004. Additionally, during 2004 we recognized $157,000 in compensation expense associated with the acceleration of stock options to a former employee. We anticipate amortization of stock-based compensation to increase in future years due to the application of SFAS No. 123(R). We are currently

evaluating the impact of SFAS No. 123(R), however we anticipate that the adoption of SFAS No. 123(R) will have a materially adverse impact on our operational results.

      Amortization of Other Acquired Intangible Assets. Amortization of other acquired intangible assets consists of the amortization of intangibles acquired as a result of certain business combinations. Amortization of other acquired intangible assets decreased $466,000 for the year ended December 31, 2005 compared to the year ended December 31, 2004, as a result of certain intangible assets being fully amortized in prior periods. We anticipate amortization of these other acquired intangible assets to continue to decrease in future periods.

      Interest and Other Income, Net. The increase in interest and other income, net of $983,000 for the year ended December 31, 2005 compared to the year ended December 31, 2004 was primarily due to increased interest earned on higher average cash and cash equivalent balances during the period coupled with higher interest rates earned during the period. We anticipate interest and other income will fluctuate in future periods as a result of our projected use of cash.

      Provision (Benefit) for Income Taxes. The increase in the tax provision of $1.2 million for the year ended December 31, 2005 compared to the year ended December 31, 2004 was primarily due to taxes on operating income earned during the year ended December 31, 2005, partially offset by certain tax credits recognized during the period. This compares to an operating loss recognized during the year ended December 31, 2004.

      Gain Share. Gain share revenue increased approximately $905,000 in 2004 compared to 2003. The increase in gain share revenue was primarily attributable to increased production volumes by our customers at new technology nodes.

      Amortization of Acquired Core Technology. The increase in amortization of acquired core technology of $3.0 million for the year ended December 31, 2004 compared to the year ended December 31, 2003 was primarily attributable to a full year of recognition and amortization of acquired core technology associated with our acquisition of IDS on September 24, 2003.

      Research and Development. The increase in research and development expenses of $1.9 million for the year ended December 31, 2004 compared to the year ended December 31, 2003 was primarily due to increased personnel-related expenses, a result of our acquisitions of IDS and WaferYield and our efforts to further advance our technology solutions through new research and development initiatives.

      Selling, General and Administrative. The increase in selling, general and administrative expenses of $2.7 million for the year ended December 31, 2004 compared to the year ended December 31, 2003 was primarily due to increases in personnel-related expenses, outside sales commissions, and legal and accounting

services related to Sarbanes-Oxley compliance activities, partially offset by a reduction in our allowance for doubtful accounts.

      Stock-Based Compensation Amortization. The decrease in stock-based compensation amortization of $1.0 million for the year ended December 31, 2004 compared to the year ended December 31, 2003 was primarily attributable to the effects of the graded vesting method of amortization that results in higher amortization expense during the initial periods following the respective option grants, partially offset by the recognition of $45,000 associated with a grant of 10,000 fully-vested stock options to a non-employee. Additionally, during 2004 we recognized $157,000 in compensation expense associated with the acceleration of stock options to a former employee.

      Amortization of Other Acquired Intangible Assets. Amortization of other acquired intangible assets increased $859,000 for the year ended December 31, 2004 compared to the year ended December 31, 2003 as a result of the recognition and amortization of acquired other intangible assets associated with our acquisition of IDS in September 2003.

      Write-off of In-process Research and Development. Write-off of in-process research and development of $800,000 in the year ended December 31, 2003 was related to the acquisition of IDS and was associated with acquired technology that had not reached technological feasibility and for which there was no alternative future use. At December 31, 2003, the acquired technology was not being developed and did not have alternative future use. Through the use of an independent valuation specialist, we determined the fair value of the acquired in-process technology by estimating the cash flows related to projects under development and the estimated revenues and operating profits related to those projects. The resulting estimated cash flows were discounted to their net present value. There was no such expense in 2004.