US Patent 12009407 Nanosheet field-effect transistor device and method of forming

A method of forming a semiconductor device includes: forming a dummy gate structure over a nanostructure, where the nanostructure overlies a fin that protrudes above a substrate, where the nanostructure comprises alternating layers of a first semiconductor material and a second semiconductor material; forming openings in the nanostructure on opposing sides of the dummy gate structure, the openings exposing end portions of the first semiconductor material and end portions of the second semiconductor material; recessing the exposed end portions of the first semiconductor material to form first sidewall recesses; filling the first sidewall recesses with a multi-layer spacer film; removing at least one sublayer of the multi-layer spacer film to form second sidewall recesses; and forming source/drain regions in the openings after removing at least one sublayer, where the source/drain regions seal the second sidewall recesses to form sealed air gaps.