X0304 4 2012-03-05 0001097864 ON SEMICONDUCTOR CORP ONNN 0001368095 Mahoney Robert Charles 5005 EAST MCDOWELL ROAD PHOENIX AZ 85008 1 Exec VP Sales & Marketing Common 2012-03-05 4 A 0 29762.0000 0.0000 A 194015.0000 D On February 16, 2012, the Compensation Committee of the Board of Directors awarded these restricted stock units to the Reporting Person under the Issuer's Amended and Restated Stock Incentive Plan ("Plan"), with an effective grant date of March 5, 2012 and vests 100% on the first anniversary of the grant date, subject to the terms and conditions of the Plan and the relevant award agreement. This award may only be settled in shares of the Issuer's common stock upon vesting. The award was for no consideration other than service as an executive officer of the Issuer. Judith A. Boyle is signing on behalf of the Reporting Person pursuant to a Power of Attorney attached hereto as an Exhibit. mahoney2012poa.txt Judith A. Boyle, Attorney-in-Fact 2012-03-07