Method of forming a gap under a source/drain feature of a multi-gate device

Abstract

Multi-gate transistor structures and methods of forming the same are provided. A method according to the present disclosure includes forming a fin-shaped structure over a substrate and including channel layers interleaved by sacrificial layers, recessing the fin-shaped structure to form a source/drain recess, recessing the sidewalls of the sacrificial layers to form inner spacer recesses, depositing a dielectric layer over the substrate and the inner spacer recesses, depositing a polymer layer over the dielectric layer, etching back the polymer layer and the dielectric layer to form inner spacer features in the inner spacer recesses and an inner spacer layer over the portion of the substrate, and epitaxially depositing more than one epitaxial layer from the sidewalls of the plurality of channel layers to form a source/drain feature in the source/drain recess. The source/drain feature and the inner spacer layer define a gap.