1
 
PROSPECTUS SUPPLEMENT NO. 6
(TO PROSPECTUS DATED NOVEMBER 10, 1997)
 
                                  $310,000,000
 
                            LAM RESEARCH CORPORATION
                   5% CONVERTIBLE SUBORDINATED NOTES DUE 2002
 
     This Prospectus Supplement supplements information contained in that
certain Prospectus dated November 10, 1997, Prospectus Supplement No. 1 to such
Prospectus dated January 27, 1998, Prospectus Supplement No. 2 to such
Prospectus dated March 20, 1998, Prospectus Supplement No. 3 to such Prospectus
dated May 14, 1998, Prospectus Supplement No. 4 to such Prospectus dated July
28, 1998, and Prospectus Supplement No. 5 to such Prospectus dated September 15,
1998 (collectively, the "Prospectus"), each relating 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, and may not be delivered or
utilized except in connection with, the Prospectus. Capitalized terms used
herein but not defined have the meanings assigned to such terms in the
Prospectus.
 
     The following information is added in the appropriate alphabetical sequence
to 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
Securityholder that may be offered pursuant to the Prospectus, as amended or
supplemented:
 

                                                                           
Allstate Insurance Company..........................   2,000,000       *     22,786       *

 
     The following line items contained in the table set forth in the Prospectus
under the caption "Selling Securityholders" are deleted in their entirety:
 

                                                                           
Merrill Lynch, Pierce, Fenner & Smith, Inc. ........   1,500,000       *     17,090       *
Silverton International Fund Limited................     900,000       *     10,254       *

 
     The line items "Deutsche Morgan Grenfell, Inc., 1,840,000, *, 20,963, *",
"Farallon Capital Institutional Partners II, L.P., 2,485,000, *, 28,312, *",
"Farallon Capital Institutional Partners III, L.P., 210,000, *, 2,392, *",
"Farallon Capital Institutional Partners, L.P., 8,900,000, 2.87%, 101,401, *",
"Farallon Capital Offshore Investors, Inc., 11,395,000, 3.68%, 129,827,*",
"Farallon Capital Partners, L.P., 9,400,000, 3.03%, 107,098, *", "North Star
Hedge Fund, L.P., 1,500,000, *, 17,090, *" and "The Common Fund, 850,000, *,
9,684, *", contained in the table set forth in the Prospectus under the caption
"Selling Securityholders" are deleted in their entirety and replaced with the
following:
 

                                                                           
Deutsche Bank Securities, Inc. (formerly Deutsche
  Morgan Grenfell, Inc.)............................   8,840,000    2.85%   100,717       *
Farallon Capital Institutional Partners II, L.P. ...   2,615,000       *     29,793       *
Farallon Capital Institutional Partners III,
  L.P. .............................................     245,000       *      2,791       *
Farallon Capital Institutional Partners, L.P. ......   9,220,000    2.97%   105,047       *
Farallon Capital Offshore Investors, Inc. ..........  12,040,000    3.88%   137,176       *
Farallon Capital Partners, L.P. ....................   9,850,000    3.18%   112,225       *
North Star Hedge Fund, L.P. ........................   1,900,000       *     21,647       *
The Common Fund.....................................     870,000       *      9,912       *

 
     The last three line items contained in the table set forth in the
Prospectus under the caption "Selling Securityholders": "Any other
holder . . .", "Notes Sold Under Registration Statement", and "Total . . ."
(other than the footnotes to the table which remain unchanged), are deleted in
their entirety and replaced with the following:
 

                                                                        
Any other holder of Notes or future transferee from any
  such holder(3)
Notes Sold Under Registration Statement.................  $216,348,000           2,464,942
          Total.........................................  $310,000,000    100%   3,531,958

 
  All information provided in this Prospectus Supplement is as of November 20,
                                     1998.
 
          THE DATE OF THIS PROSPECTUS SUPPLEMENT IS NOVEMBER 23, 1998.