Patent ID: 6849485

Claim:
A method of forming a thin gate insulator layer for a dual gate insulator, metal oxide semiconductor field effect transistor (MOSFET) device, on a semiconductor substrate, comprising the steps of: providing a portion of said semiconductor substrate surrounded by insulator filled, shallow trench isolation (STI) regions, to be used as an active device region; forming a first insulator layer on a first area of said active device region, leaving a second area of said active device region bare; performing a procedure to form a thin gate insulator layer on said second area of said active device region, with said procedure converting said first insulator layer located on said first area of said active device region to a thicker second insulator layer; and performing a definition procedure to form a conductive gate structure overlying a first portion of said thin gate insulator layer while a second portion of said thin gate insulator layer not covered by said conductive gate structure is removed and with said second insulator layer protecting said first area of said active device region thinned during said definition procedure.