SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D. C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

January 31, 2008

Date of report (Date of earliest event reported)

ON Semiconductor Corporation

(Exact name of registrant as specified in its charter)

Delaware	000-30419	36-3840979
(State or other jurisdiction of incorporation)	(Commission File Number)	(I.R.S. Employer Identification Number)

ON Semiconductor Corporation 5005 E. McDowell Road Phoenix, Arizona	85008
(Address of principal executive offices)	(Zip Code)

602-244-6600

(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

x Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 2.02. Results of Operations and Financial Condition.

On January 31, 2008, ON Semiconductor Corporation (“ON”) announced in a news release its financial performance for the quarter and year ended December 31, 2007. A copy of ON Semiconductor Corporation’s news release is attached hereto as EXHIBIT 99.1.

Item 8.01. Other Events.

As noted above, on January 31, 2008, ON announced in a news release its financial performance for the quarter and year ended December 31, 2007. Within this news release, ON has made reference to its proposed acquisition of AMIS Holdings, Inc. (“AMIS”). See below for important additional information on this proposed acquisition. A copy of ON Semiconductor Corporation’s news release is attached hereto as EXHIBIT 99.1.

IMPORTANT ADDITIONAL INFORMATION

In connection with ON’s proposed acquisition of AMIS Holdings, Inc. (“AMIS”), ON has filed with the SEC a preliminary Registration Statement on Form S-4 containing a Joint Proxy Statement/Prospectus. Once finalized, the definitive Joint Proxy Statement/ Prospectus will be mailed to stockholders of ON and AMIS. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE JOINT PROXY STATEMENT/PROSPECTUS AND OTHER DOCUMENTS FILED WITH THE SEC CAREFULLY IN THEIR ENTIRETY WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION.

Investors and security holders will be able to obtain free copies of the Registration Statement and the Joint Proxy Statement/Prospectus (when available) and other documents filed with the SEC by ON and AMIS through the web site maintained by the SEC at www.sec.gov. In addition, investors and security holders will be able to obtain free copies of the Registration Statement and the Joint Proxy Statement/Prospectus (when available) 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: (602) 244-3437) 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: 208-233-4690) or going to AMIS’ corporate website at www.amis.com.

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 will be included in the definitive Joint Proxy Statement/Prospectus and the other relevant documents filed with the SEC (when available).

Item 9.01. Financial Statements and Exhibits.

(a) Financial Statements of Businesses Acquired

Not applicable.

(b) Pro Forma Financial Information

Not applicable.

(c) Shell Company Transactions

Not applicable.

(d) Exhibits

Exhibit No.	Description
99.1	News release for ON Semiconductor Corporation dated January 31, 2008, announcing financial performance for the quarter and year ended December 31, 2007

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

	ON SEMICONDUCTOR CORPORATION (Registrant)
Date: January 31, 2008	By:	/s/ DONALD A. COLVIN
		Donald A. Colvin
		Executive Vice President and Chief Financial Officer

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EXHIBIT INDEX

Exhibit No.	Description
99.1	News release for ON Semiconductor Corporation dated January 31, 2008, announcing financial performance for the quarter and year ended December 31, 2007

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