Patent ID: 7696036

Claim:
A method of forming a semiconductor structure comprising: forming a first gate stack and a second gate stack on a semiconductor substrate, wherein said first gate stack comprises a first high-k dielectric portion vertically abutting said semiconductor substrate, and said second gate stack comprises a second high-k dielectric portion vertically abutting said semiconductor substrate; forming a gate sidewall nitride directly on sidewalls of said first gate stack; forming an oxide spacer directly on sidewalls of said second gate stack; and subjecting said first gate stack and said second gate stack to an anneal in an oxygen environment, wherein oxygen content within said second high-k dielectric portion increases substantially, while the oxygen content of said first high-k dielectric portion does not increase substantially during said anneal, wherein said first high-k dielectric portion comprises a first dielectric metal oxide containing a metal and said second high-k dielectric portion comprises a second dielectric metal oxide containing the same metal, and wherein said first high-k dielectric portion and said second high-k dielectric portion comprise substantially the same oxygen content during said forming of said first gate stack and said second gate stack.