ON Semiconductor and AMIS Holdings, Inc. Proposed Merger Registration Statement Declared Effective

  
    
  
  
    
      ON Semiconductor Corporation (NASDAQ: ONNN) and AMIS Holdings, Inc. 
      (NASDAQ: AMIS), parent company of AMI Semiconductor, today announced 
      that the Securities and Exchange Commission has declared effective the 
      Registration Statement on Form S-4 relating to the proposed merger 
      between ON Semiconductor Corporation and AMIS Holdings. As previously 
      announced, ON and AMIS Holdings have entered into a definitive merger 
      agreement under which ON would acquire AMIS Holdings in a 
      stock-for-stock merger. Under the terms of the agreement, each 
      outstanding share of AMIS Holdings common stock would be exchanged for 
      1.15 shares of ON common stock.
    
    
      ON Semiconductor stockholders of record as of the close of business on 
      Jan. 25, 2008 will be mailed the definitive joint proxy 
      statement/prospectus in connection with the proposed merger with AMIS 
      Holdings and will be entitled to vote at the special meeting of ON 
      Semiconductor stockholders. The special meeting of ON stockholders to 
      consider and vote upon the proposed merger with AMIS Holdings has been 
      scheduled for March 12, 2008 at 9:30 a.m., local time, at the principal 
      executive offices of ON Semiconductor, 5005 East McDowell Road, Phoenix, 
      AZ 85008. The transaction is expected to close as soon as practicable 
      under the terms and conditions of the merger agreement, which include, 
      among other things, a requirement that each of ON’s 
      and AMIS’ stockholders approve the merger.
    
    
      ON Semiconductor stockholders are encouraged to read the definitive 
      joint proxy statement/prospectus in its entirety as it provides, among 
      other things, a detailed discussion of the process that led to the 
      proposed merger and the reasons behind ON's Board of Directors' 
      recommendation that ON stockholders vote FOR the amendment to ON’s 
      certificate of incorporation and issuance of securities in connection 
      with the merger.
    
    
      As previously announced on Jan. 31, 2008, the waiting period under the 
      Hart-Scott-Rodino Antitrust Improvements Act of 1976 has expired with 
      respect to, and the German Federal Cartel Office provided clearance for, 
      the proposed merger.
    
    
      About ON Semiconductor
    
    
      With its global logistics network and strong portfolio of power 
      semiconductor devices, ON Semiconductor (NASDAQ: ONNN) is a preferred 
      supplier of power solutions to engineers, purchasing professionals, 
      distributors and contract manufacturers in the power supply, computer, 
      cell phone, portable devices, automotive and industrial markets. For 
      more information, please visit ON Semiconductor's website at http://www.onsemi.com.
    
    
      About AMI Semiconductor
    
    
      AMI Semiconductor (NASDAQ: AMIS) is a leader in the design and 
      manufacture of silicon solutions for the real world. As a widely 
      recognized innovator in state-of-the-art mixed-signal and digital 
      products, AMIS is committed to providing customers in the automotive, 
      medical, industrial, mil/aero, and communication markets with the 
      optimal value, quickest time-to-market semiconductor solutions. AMI 
      Semiconductor operates globally with headquarters in Pocatello, Idaho, 
      European corporate offices in Oudenaarde, Belgium, and a network of 
      sales and design centers located in the key markets of the North 
      America, Europe and the Asia Pacific region. For more information, 
      please visit the AMIS Web site at www.amis.com.
    
    
      This document contains forward-looking statements within the meaning of 
      the Private Securities Litigation Reform Act of 1995. These 
      forward-looking statements include, but are not limited to, statements 
      related to the benefits of the proposed transaction between ON 
      Semiconductor Corporation (“ON”) 
      and AMIS Holdings, Inc. (“AMIS”) 
      and the future financial performance of ON. These forward-looking 
      statements are based on information available to ON and AMIS as of the 
      date of this release and current expectations, forecasts and assumptions 
      and involve a number of risks and uncertainties that could cause actual 
      results to differ materially from those anticipated by these 
      forward-looking statements. Such risks and uncertainties include a 
      variety of factors, some of which are beyond ON’s 
      or AMIS’ control. In particular, such risks 
      and uncertainties include difficulties encountered in integrating merged 
      businesses; the risk that the transaction does not close, including the 
      risk that the requisite stockholder and regulatory approvals may not be 
      obtained; the variable demand and the aggressive pricing environment for 
      semiconductor products; dependence on each company’s 
      ability to successfully manufacture in increasing volumes on a 
      cost-effective basis and with acceptable quality its current products; 
      the adverse impact of competitive product announcements; revenues and 
      operating performance, changes in overall economic conditions, the 
      cyclical nature of the semiconductor industry, changes in demand for our 
      products, changes in inventories at customers and distributors, 
      technological and product development risks, availability of raw 
      materials, competitors' actions, pricing and gross margin pressures, 
      loss of key customers, order cancellations or reduced bookings, changes 
      in manufacturing yields, control of costs and expenses, significant 
      litigation, risks associated with acquisitions and dispositions, risks 
      associated with leverage and restrictive covenants in debt agreements, 
      risks associated with international operations, the threat or occurrence 
      of international armed conflict and terrorist activities both in the 
      United States and internationally, risks and costs associated with 
      increased and new regulation of corporate governance and disclosure 
      standards (including pursuant to Section 404 of the Sarbanes-Oxley Act 
      of 2002), and risks involving environmental or other governmental 
      regulation. Information concerning additional factors that could cause 
      results to differ materially from those projected in the forward-looking 
      statements is contained in ON’s Annual Report 
      on Form 10-K as filed with the Securities and Exchange Commission (the “SEC”) 
      on February 23, 2007, Quarterly Reports on Form 10-Q, Current Reports on 
      Form 8-K and other of ON’s SEC filings, and 
      AMIS’ Annual Report on Form 10-K as filed 
      with the SEC on February 28, 2007, Quarterly Reports on Form 10-Q, 
      Current Reports on Form 8-K and other of AMIS’ 
      SEC filings. These forward-looking statements should not be relied upon 
      as representing ON’s or AMIS’ 
      views as of any subsequent date and neither undertake any obligation to 
      update forward-looking statements to reflect events or circumstances 
      after the date they were made.
    
    
      This communication is being made in respect of the proposed transaction 
      involving ON and AMIS. In connection with the proposed transaction, ON 
      has filed with the SEC a Registration Statement on Form S-4 (File No. 
      333-148630), as amended, containing a joint proxy statement/prospectus 
      and each of ON and AMIS have filed with the SEC other documents 
      regarding the proposed transaction. The joint proxy statement/prospectus 
      will be mailed to stockholders of ON and AMIS on or about February 11, 
      2008. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE JOINT PROXY 
      STATEMENT/PROSPECTUS AND OTHER DOCUMENTS FILED WITH THE SEC CAREFULLY IN 
      THEIR ENTIRETY BECAUSE THEY CONTAIN IMPORTANT INFORMATION ABOUT THE 
      PROPOSED TRANSACTION.
    
    
      Investors and security holders may obtain free copies of the 
      registration statement and the joint proxy statement/prospectus and 
      other documents filed with the SEC by ON and AMIS through the website 
      maintained by the SEC at www.sec.gov. 
      In addition, investors and security holders may obtain free copies of 
      the registration statement and the joint proxy statement/prospectus and 
      other documents filed with the SEC from ON by directing a request to ON 
      Semiconductor Corporation, 5005 East McDowell Road, Phoenix, AZ, 85008, 
      Attention: Investor Relations (telephone: [phone]) or going to ON’s 
      corporate website at www.onsemi.com, 
      or from AMIS by directing a request to AMIS Holdings, Inc., 2300 
      Buckskin Road Pocatello, ID, 83201, Attention: Investor Relations 
      (telephone: [phone]) or going to AMIS’ 
      corporate website at www.amis.com. ON 
      Semiconductor stockholders needing assistance with voting may also 
      contact ON Semiconductor’s proxy advisor, 
      MacKenzie Partners, Inc., at [phone]. AMIS stockholders needing 
      assistance with voting may contact AMIS’ 
      proxy solicitation firm, The Altman Group, at [phone].
    
    
      ON and AMIS, and their respective directors and executive officers, may 
      be deemed to be participants in the solicitation of proxies in respect 
      of the proposed transaction. Information regarding ON’s 
      directors and executive officers is contained in its annual proxy 
      statement filed with the SEC on April 11, 2007. Information regarding 
      AMIS’ directors and executive officers is 
      contained in AMIS’ annual proxy statement 
      filed with the SEC on May 24, 2007. Additional information regarding the 
      interests of such potential participants is included in the joint proxy 
      statement/prospectus and the other relevant documents filed with the SEC 
      (when available).
    
    
      ON Semiconductor and the ON Semiconductor logo are registered 
      trademarks of Semiconductor Components Industries, LLC. All other brand 
      and product names appearing in this document are registered trademarks 
      or trademarks of their respective holders. Although the company 
      references its website in this news release, information on the website 
      is not to be incorporated herein.