Semiconductor devices and methods of manufacturing thereof

A semiconductor device, comprising:

• a first nanostructure extending along a first direction;
• an epitaxial structure coupled to one end of the first nanostructure;
• a gate structure extending along a second direction perpendicular to the first direction, wherein the gate structure wraps around the first nanostructure;
• a first inner spacer interposed between a first portion of the gate structure and the epitaxial structure along the first direction;
• and
• a first silicon-based cap layer and a second silicon-based cap layer;
• wherein the first silicon-based cap layer is in contact with a top surface of the first inner spacer, and interposed between the first portion of the gate structure and the epitaxial structure along the first direction;
• and
• wherein the second silicon-based cap layer is in contact with a bottom surface of the first inner spacer, and interposed between the first portion of the gate structure and the epitaxial structure along the first direction.

A method for fabricating semiconductor devices, comprising:

• forming a stack including a plurality of first nanostructures and a plurality of second nanostructures alternately stacked on top of one another, wherein each of the plurality of first and second nanostructures extends along a first direction;
• forming a first gate structure traversing the stack, wherein the first gate structure extends along a second direction perpendicular to the first direction;
• inwardly etching end portions of each of the plurality of second nanostructures to form a plurality of recesses;
• forming a silicon-based cap layer lining each of the plurality of recesses;
• forming a plurality of inner spacers to fill the plurality of recesses, respectively;
• removing respective remaining portions of the plurality of second nanostructures and the first gate structure, concurrently with removing a portion of the silicon-based cap layer;
• and
• forming a second gate structure wrapping around each of the plurality of first nanostructures.