Semiconductor devices and methods of manufacturing thereof

Abstract

A method includes forming a fin structure over a substrate, the fin structure including alternating first semiconductor layers and second semiconductor layers stacked along a vertical direction; forming a dummy gate structure over the fin structure; selectively depositing an outer spacer layer on the dummy gate structure; performing a plasma doping process to form source/drain regions in each second semiconductor layer adjacent the dummy gate structure, where a portion of each second semiconductor layer interposing between the source/drain regions defines a channel region; forming a dielectric layer over the fin structure; removing the dummy gate structure to form a gate trench in the dielectric layer; selectively removing the first semiconductor layers to form openings interleaved with the second semiconductor layers; and forming a metal gate structure to fill the gate trench and the openings.