Semiconductor device and manufacturing method thereof

A semiconductor device, comprising:

• a first fin and a second fin, the first fin having a channel region comprising at plurality of channel sheet layers and a plurality of metal gate layers;
• a separating wall and a plurality of liners including a first liner and a second liner formed between the first fin and the second fin, wherein the first liner is closer to at least one metal gate layer of the plurality of metal gate layers and the second liner is closer to the separating wall;
• and
• inner spacer material formed around the at least one metal gate layer, the first liner, and the second liner;
• wherein the at least one metal gate layer has a first critical dimension (CD) measured between the inner spacer material at an end closest to a first liner, and the first liner has a second CD measured between the inner spacer material that is approximately equal to the first CD.

A fabrication method, comprising:

• forming a first fin and a second fin, the first fin having an epitaxial stack comprising at least one sacrificial epitaxial layer and at least one channel epitaxial layer;
• forming a separating wall and a plurality of liners including a first liner and a second liner between the first fin and the second fin, wherein the first liner is closer to the at least one sacrificial epitaxial layer of the first fin and the second liner is closer to the separating wall;
• forming a sacrificial gate stack over channel regions of the first fin;
• recessing the at least one sacrificial epitaxial layer to form a cavity;
• recessing the first liner, after recessing the at least one sacrificial epitaxial layer, thereby expanding the cavity;
• recessing the second liner, after recessing the first liner, thereby expanding the cavity;
• forming inner spacer material in the cavity;
• forming source/drain features;
• and
• replacing the sacrificial gate stack and the at least one sacrificial epitaxial layer with a metal gate;
• wherein the metal gate has a first critical dimension (CD) measured between the inner spacer material, the first liner has a second CD measured between the inner spacer material, and the second liner has a third CD measured between the inner spacer material.