Gate electrode architecture for improved work function tuning and method of manufacture

Abstract

A method of forming gate electrodes having different work functions includes forming a first well of a first conductivity type and a second well of a second conductivity type. Subsequently, a gate dielectric layer is deposited over the first and second wells. A multi-layer stack comprising two or more thin metal/metal nitride layers is next formed over the first well. A thick metal/metal nitride layer is formed over the multi-layer stack to form the first gate electrode. The thick metal/metal nitride layer is also formed over the gate dielectric layer portion extending over the second well, thereby forming the second gate electrode. The first and second electrodes are then annealed, and thereafter exhibit different work functions as desired.