Multi-gate field-effect transistors and methods of forming the same

Abstract

A method of forming a semiconductor structure includes forming a fin structure having a stack of alternating first semiconductor layers and second semiconductor layers over a substrate, forming cladding layers along sidewalls of the fin structure, forming a dummy gate stack over the cladding layers, and forming source/drain (S/D) features in the fin structure and adjacent to the dummy gate stack. The method further includes removing the dummy gate stack to form a gate trench adjacent to the S/D features, removing the cladding layers to form first openings along the sidewalls of the fin structure, where the first openings extend to below the stack, removing the first semiconductor layers to form second openings between the second semiconductor layers and adjacent to the first openings, and subsequently forming a metal gate stack in the gate trench, the first openings, and the second openings.