Gate-all-around structure and methods of forming the same

A device comprising:

• a first plurality of semiconductor layers disposed over a first portion of a semiconductor fin protruding from a substrate;
• a second plurality of semiconductor layers disposed over a second portion of the semiconductor fin protruding from the substrate;
• a first gate dielectric layer wrapping around at least one semiconductor layer from the first plurality of semiconductor layers;
• a first gate electrode wrapping around the first gate dielectric layer disposed on the at least one semiconductor layer from the first plurality of semiconductor layers;
• a source/drain feature interfacing with the at least one semiconductor layer from the first plurality of semiconductor layers;
• and
• a dielectric inner spacer including a first portion extending from the at least one semiconductor layer from the first plurality of semiconductor layers to one of the semiconductor layer from the second plurality of semiconductor layers,
• wherein the dielectric inner spacer covers a top surface of the source/drain feature.

A method comprising:

• forming a fin over a substrate, wherein the fin includes a plurality of semiconductor layers disposed over a channel region and a source/drain region of the substrate;
• removing a portion of the fin in the source/drain region of the substrate to form a trench therein;
• selectively removing portions from at least one of semiconductor layer from the plurality of semiconductor layers in the channel region of the substrate to form at least one recessed semiconductor layer in the channel region;
• forming a material layer directly on the at least one recessed semiconductor layer and in the trench;
• forming a source/drain feature on the material layer disposed in the trench;
• and
• after forming the source/drain feature, converting the material layer to a dielectric material layer.