Patent ID: 6602751
Filing Date: 2003-08-05
Classification: H01L,Y10S

Abstract:
A semiconductor device manufacturing method for forming three kinds of metal oxide semiconductor transistors having a first gate oxide film with a small film thickness, a second gate oxide film with a medium film thickness, and a third gate oxide film with a large film thickness respectively on a semiconductor substrate, said method comprising:an initial gate oxide film forming step for forming an initial gate oxide film with a large film thickness on said semiconductor substrate; an initial gate oxide film removing step, using a first photo-resist, for selectively removing said initial gate oxide film in a first region wherein said first gate oxide film is to be formed on said semiconductor substrate and in a second region wherein said second gate oxide film is to be formed on said semiconductor substrate; removing said first photo-resist using a process causing formation of a chemical oxide film in said first and second regions; applying a second photo-resist exposing only said second region wherein said second photoresist is applied over said chemical oxide layer in said first region and over said initial gate oxide film in said third region; a fluorine ion implanting step for selectively implanting ions of fluorine in said second region on said semiconductor substrate in accordance with said second photo-resist through said chemical oxide layer wherein said fluorine ions are implanted in a fluorine implanted layer at a comparatively shallow portion of said semiconductor substrate in said second region; and an oxidation processing step for simultaneously forming said first gate oxide film and said second gate oxide film in said first region and said second region on said semiconductor substrate, respectively.