Inner spacer formation in multi-gate transistors

Abstract

A method for forming a semiconductor structure includes forming a fin on a semiconductor substrate. The fin includes channel layers and sacrificial layers stacked one on top of the other in an alternating fashion. The method also includes removing a portion of the fin to form a first opening and expose vertical sidewalls of the channel layers and the sacrificial layers, epitaxially growing a source/drain feature in the first opening from the exposed vertical sidewalls of the channel layers and the sacrificial layers, removing another portion of the fin to form a second opening to expose a vertical sidewall of the source/drain feature, depositing a dielectric layer in the second opening to cover the exposed vertical sidewall of the source/drain feature, and replacing the sacrificial layers with a metal gate structure in the second opening. The dielectric layer separates the source/drain feature from contacting the metal gate structure.