Patent ID: 7691701

Claim:
A method of forming gate stacks for field-effect-transistors, the method comprising: forming a metal-containing layer directly on a first titanium-nitride (TiN) layer, said first TiN layer covering areas of a semiconductor substrate designated for first and second types of field-effect-transistors; forming a capping layer of a second TiN layer on top of said metal-containing layer; patterning said second TiN layer and said metal-containing layer to cover only a first portion of said first TiN layer, said first portion of said first TiN layer covering an area designated for said first type of field-effect-transistors; etching away a second portion of said first TiN layer exposed by said patterning while protecting said first portion of said first TiN layer, from said etching, through covering with at least a portion of thickness of said patterned metal-containing layer; and forming a third TiN layer covering an area of said semiconductor substrate designated for said second type of field-effect-transistors.