X0303 4 2009-11-04 0001097864 ON SEMICONDUCTOR CORP ONNN 0001364109 Williams Michael Andrew 5005 EAST MCDOWELL ROAD PHOENIX AZ 85008 1 SVP & GM, Auto & Pwr Grp Common 2009-11-04 4 A 0 19724 0 A 85406.568 D Common 2009-11-04 4 F 0 6298 6.83 D 79108.568 D This transaction reports the acquisition, effective November 4, 2009, of 19,724 shares of common stock resulting from the attainment of a performance goal under an earlier Performance Based Restricted Stock Units Award ("PBRSU Award"), as described more below. The Compensation Committee of the Issuer originally awarded 236,687 PBRSUs to the Reporting Person with an effective grant date of March 2, 2009 subject to the Issuers 2000 Stock Incentive Plan and a related award agreement. The PBRSU Award will vest, generally, over a three-year (twelve quarter) period but only upon the Issuer achieving certain adjusted non-GAAP earnings before interest, taxes, depreciation and amortization ("EBITDA") base and target performance measurements as set forth in the PBRSU Award agreement. Balance stated includes 46.934 shares acquired by Reporting Person under Issuer's Employee Stock Purchase Plan from 7/1/09 through 9/30/09. This transaction reports the disposition of shares of common stock withheld by the Issuer in connection with the vesting of the PBRSU Award explained in (1) above. This withholding is pursuant to the related award agreement in order to satisfy the Reporting Person's tax obligations due upon the vesting of the units. The Issuer will pay the taxes on behalf of the Reporting Person. Judith A. Boyle is signing on behalf of the Reporting Person pursuant to a Power of Attorney attached herein as an Exhibit. williams2009poa.TXT Judith A. Boyle, Attorney-in-Fact 2009-11-06