1 FILED PURSUANT TO RULE 424(b)(3) REGISTRATION STATEMENT NO. 333-39167 PROSPECTUS SUPPLEMENT NO. 7 (TO PROSPECTUS DATED NOVEMBER 10, 1997) $310,000,000 LAM RESEARCH CORPORATION 5% CONVERTIBLE SUBORDINATED NOTES DUE 2002 This Prospectus Supplement replaces information contained in that certain Prospectus dated November 10, 1997 and supersedes Prospectus Supplement No. 1 through Prospectus Supplement No. 6 to such Prospectus, which prior supplements should be discarded. The Prospectus dated November 10, 1997 and this Supplement No. 7 (collectively the "Prospectus") relate to the potential sale from time to time of up to $310,000,000 aggregate amount of Notes and the Common Stock issuable upon conversion thereof by the Selling Securityholders. This Prospectus Supplement is not complete without the Prospectus. This Prospectus Supplement may not be delivered or utilized without the Prospectus. Capitalized terms used in this Prospectus Supplement but not defined have the meanings contained in the Prospectus. The following information replaces the table set forth in the Prospectus under the caption "Selling Securityholders" with respect to the Selling Securityholders and the respective principal amounts of Registrable Notes beneficially owned by such Selling Securityholders that may be offered pursuant to the Prospectus, as amended or supplemented: SHARES THAT PERCENTAGE OF PRINCIPAL MAY BE SOLD COMMON STOCK AMOUNT OF PERCENTAGE OF PURSUANT TO AFTER NOTES THAT MAY NOTES THIS CONVERSION OF NAME BE SOLD ($) OUTSTANDING PROSPECTUS (1) THE NOTES (2) ---- ----------- ----------- -------------- ------------- Allstate Insurance Company 2,000,000 * 22,786 * Associated Electric & Gas 250,000 * 2,848 * Insurance Services BancAmerica Robertson Stephens 2,040,000 * 23,242 * Bear, Stearns Securities Corp. 2,300,000 * 26,204 * Berger Balanced Fund, A 200,000 * 2,278 * Series of the Berger Investment Portfolio Trust Boston College Endowment Fund 106,000 * 1,207 * The Common Fund 870,000 * 9,912 *

2 SHARES THAT PERCENTAGE OF PRINCIPAL MAY BE SOLD COMMON STOCK AMOUNT OF PERCENTAGE OF PURSUANT TO AFTER NOTES THAT MAY NOTES THIS CONVERSION OF NAME BE SOLD ($) OUTSTANDING PROSPECTUS (1) THE NOTES (2) ---- ----------- ----------- -------------- ------------- Consolidated Press 2,570,000 * 29,281 * International, Ltd. Deeprock & Co. 2,500,000 * 28,483 * Deutsche Bank New York 10,250,000 3.31% 116,782 * Custody Services Deutsche Bank Securities, Inc. 8,840,000 2.85% 100,717 * Emory University Endowment 470,425 * 5,359 * Fund Employers' Reinsurance 200,000 * 2,278 * Corporation Everen Securities, Inc. 265,000 * 3,019 * Farallon Capital 9,220,000 2.97% 105,047 * Institutional Partners, L.P. Farallon Capital 2,615,000 * 29,793 * Institutional Partners II, L.P. Farallon Capital 245,000 * 2,791 * Institutional Partners III, L.P. Farallon Capital Offshore 12,040,000 3.88% 137,176 * Investors, Inc. Farallon Capital Partners, 9,850,000 3.18% 112,225 * L.P. The George Putnam Fund of 1,000,000 * 11,393 * Boston Goldman Sachs & Co. 900,000 * 10,254 * Highbridge Capital Corp. 2,000,000 * 22,786 * Janus Balanced Funds and 5,500,000 1.77% 62,663 * Janus Aspen Balanced Portfolio MainStay Convertible Fund 3,500,000 1.13% 39,876 * McMahan Securities Company, 151,000 * 1,720 * L.P. Museum of Fine Arts, Boston 123,000 * 1,401 * -2-

3 SHARES THAT PERCENTAGE OF PRINCIPAL MAY BE SOLD COMMON STOCK AMOUNT OF PERCENTAGE OF PURSUANT TO AFTER NOTES THAT MAY NOTES THIS CONVERSION OF NAME BE SOLD ($) OUTSTANDING PROSPECTUS (1) THE NOTES (2) ---- ----------- ----------- -------------- ------------- NationsBanc Montgomery 2,000,000 * 22,786 * Securities, Inc./ San Francisco Nesbitt Burns 1,187,000 * 13,523 * New Hampshire State 546,000 * 6,220 * Retirement System North Star Hedge Fund, L.P. 1,900,000 * 21,647 * Promutual 458,000 * 5,218 * Putnam Convertible 299,000 * 3,406 * Opportunities and Income Trust Putnam Convertible 550,000 * 6,266 * Income-Growth Trust Putnam Funds Trust - Putnam 15,000 * 170 * High Yield Total Return Fund Putnam High Income 300,000 * 3,418 * Convertible and Bond Fund Putnam High Yield Fixed 100,000 * 1,139 * Income Fund, LLC Putnam High Yield Advantage 5,000,000 1.61% 56,967 * Fund Putnam High Yield Trust 4,000,000 1.29% 45,573 * Putnam Income Fund 1,500,000 * 17,090 * Putnam Variable Trust - 900,000 * 10,254 * Putnam VT High Yield Fund Shephard Investment 7,245,000 2.34% 82,545 * International, Ltd. Societe Generale Securities 2,400,000 * 27,344 * Corp. SoundShore Partners, L.P. 2,000,000 * 22,786 * STI Classic Mid Cap Fund 5,237,075 1.69% 59,668 * STI Classic Mid Cap Variable 290,000 * 3,304 * Annuity Trust -3-

4 SHARES THAT PERCENTAGE OF PRINCIPAL MAY BE SOLD COMMON STOCK AMOUNT OF PERCENTAGE OF PURSUANT TO AFTER NOTES THAT MAY NOTES THIS CONVERSION OF NAME BE SOLD ($) OUTSTANDING PROSPECTUS (1) THE NOTES (2) ---- ----------- ----------- -------------- ------------- Tinicum Partners, L.P. 190,000 * 2,164 * Tribeca Investments, LLC 2,000,000 * 22,786 * University of Rochester 108,000 * 1,230 * Any other holder of Notes or future transferee from any such holder (3) $217,713,000 2,480,494 Total $310,000,000 100% 3,531,958 * Less than one percent. - ---------- (1) Assumes conversion of the full amount of Notes held by such Selling Securityholder at the initial conversion price of $87.77 per share. The conversion price is subject to adjustment as described under "Description of Notes -- Conversion Rights." Fractional shares will not be issued upon conversion of the Notes. Cash will be paid in lieu of fractional shares, if any. The difference in the total from the total set forth on the Prospectus Cover page is due to the rounding of fractional shares. (2) The percentage of Common Stock after conversion of the Notes: (1) assumes that the Selling Securityholders do not beneficially own any Common Stock other than the Common Stock issuable upon conversion of the Notes at the initial conversion rate; and (2) represents the percentage of the Common Stock each Selling Securityholder will have after treating as outstanding the number of shares of Common Stock shown as being issuable upon the assumed conversion by the named Selling Securityholder of the full amount of such holder's Notes but not assuming the conversion of the Notes of any other Selling Securityholder. These percentages are based on 37,634,584 shares of Common Stock that were issued and outstanding as of November 7, 1997 before taking into account any of the assumed conversions. (3) Certain Selling Securityholders, while reserving the right to have their Notes registered at a later date, have either: (1) elected to not have Notes owned by them registered at this time; or (2) have not provided the Company with instructions to register their Notes at this time. -4-

5 Information concerning other selling holders of the Notes will be set forth from time to time in Prospectus Supplements, if required. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Information concerning the Selling Securityholders may change from time to time. The Company will prepare additional supplements to the Prospectus to show changed information when necessary. The per share conversion price and the number of shares issuable upon conversion of the Notes is subject to adjustment under certain circumstances. The aggregate number of shares of Common Stock issuable upon conversion of the Notes offered hereby may increase or decrease if there is an adjustment in the conversion price. -5-