Patent ID: 7118974

Claim:
A method of forming three different gate oxide thicknesses on a substrate comprising: (a) providing a substrate with isolation regions that separate active areas where circuits are to be formed, with one said active area having a nitrogen implant near the substrate surface, (b) growing a first oxide layer on active areas of said substrate, (c) removing selected portions of the first oxide layer including the oxide over the nitridated active area, (d) growing a second oxide layer on active areas of said substrate, (e) annealing said substrate, (f) nitridating all oxide regions, and (g) annealing said substrate; wherein the first oxide layer is comprised of an HfO 2 /silicate layer which is formed by first growing an SiO 2 layer with a thickness of about 3 Angstroms using an RTO method followed by depositing an HfO 2 /silicate later with a thickness in a range of 2 to 30 Angstroms.