UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K/A

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of The Securities Exchange Act of 1934

September 19, 2016

Date of report (Date of earliest event reported)

ON Semiconductor Corporation

(Exact name of registrant as specified in its charter)

(602) 244-6600

(Registrant’s telephone number, including area code)

Not applicable

(Former name or former address, if changed since last report.)

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:

EXPLANATORY NOTE

As previously disclosed, on November 18, 2015, ON Semiconductor Corporation (the “Company”) entered into that certain Agreement and Plan of Merger (the “Merger Agreement”), by and among the Company, Falcon Operations Sub, Inc. (“Purchaser”) and Fairchild Semiconductor International, Inc. (“Fairchild”), pursuant to which Purchaser commenced a cash tender offer (the “Offer”) to acquire all of the outstanding shares of Fairchild’s common stock, par value $0.01 per share (the “Shares”), for $20.00 per share in cash, without interest, upon the terms and subject to the conditions set forth in the Offer to Purchase dated December 4, 2015 and the related Letter of Transmittal.

As previously reported under Item 2.01 of the Current Report on Form 8-K filed by the Company on September 19, 2016, pursuant to the terms and conditions of the Merger Agreement, on September 19, 2016, Purchaser merged with and into Fairchild, with Fairchild surviving as a wholly owned subsidiary of the Company (the “Merger”). At the effective time of the Merger, each Share outstanding was converted into the right to receive $20.00 in cash, without interest and less any required withholding taxes (other than Shares held by Fairchild as treasury stock, or the Company, Fairchild or their respective wholly owned subsidiaries (including Purchaser), which Shares were cancelled and ceased to exist).

The results of Fairchild have been included in the Company’s consolidated financial statements since the date of acquisition.

This Current Report on Form 8-K/A amends the Form 8-K filed on September 19, 2016 to provide the historical financial statements of Fairchild required under Item 9.01(a) and the pro forma financial information required under Item 9.01(b).

The audited financial statements of Fairchild as of December 27, 2015 and December 28, 2014, and for the three years ended December 27, 2015 are included as Exhibit 99.1 to this Current Report on Form 8-K/A and are incorporated by reference herein.

The unaudited financial statements of Fairchild as of and for the three and six month periods ended June 26, 2016 are included as Exhibit 99.2 to this Current Report on Form 8-K/A and are incorporated by reference herein.

The consent of Fairchild’s independent auditors is attached hereto as Exhibit 23.1.

The unaudited pro forma condensed combined statements of operations of the Company and Fairchild with respect to the year ended December 31, 2015 and the six months ended July 1, 2016 are included as Exhibit 99.3 to this Current Report on Form 8-K/A and are incorporated by reference herein.

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 hereunto duly authorized.

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