Semiconductor device and manufacture method thereof

Abstract

Semiconductor devices and methods of forming the same are provided. An exemplary method includes forming a plurality of nanostructures over a substrate, forming a first source / drain feature coupled to a bottommost nanostructure of the plurality of nanostructures, forming a second source / drain feature coupled to a topmost nanostructure of the plurality of nanostructures, forming a first gate structure wrapping around the bottommost nanostructure, and forming a second gate structure wrapping around the topmost nanostructure, where the second gate structure comprises an aluminum-containing n-type work function layer, the first gate structure comprises a first p-type work function layer, a second p-type work function layer, and a diffusion barrier layer disposed between the first p-type work function layer and the second p-type work function layer, wherein an aluminum concentration of the first p-type work function layer is less than an aluminum concentration of the second p-type work function layer.

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