Metal gate structures of semiconductor devices

Abstract

A method of fabricating a semiconductor device includes forming first and second nanostructured layers arranged in an alternating configuration on a substrate, forming first and second nanostructured channel regions in the first nanostructured layers, forming first and second gate-all-around structures wrapped around each of the first and second nanostructured channel regions. The forming the GAA structures includes depositing first and second gate barrier layers having similar material compositions and work function values on the first and second gate dielectric layers, forming first and second diffusion barrier layers on the first and second gate barrier layers, and doping the first and second gate barrier layers from a dopant source layer through the first and second diffusion barrier layers. The first diffusion barrier layer is thicker than the second diffusion barrier layer and the doped first and second gate barrier layers have work function values and doping concentrations different from each other.