Field effect transistor having gate contact and source/drain contact separated by a gap

A semiconductor device, comprising:

• a fin extending from a substrate and lengthwise along a direction, the fin comprising a channel region and a source/drain region adjacent to the channel region;
• a gate structure over the channel region;
• a gate cap layer over the gate structure;
• a first sealing layer disposed over and in contact with the gate cap layer;
• a gate contact via extending through the first sealing layer to couple to the gate cap layer, sidewalls of the gate contact via being in direct contact with the first sealing layer;
• a silicide layer disposed over the source/drain region;
• a source/drain contact over the silicide layer;
• a source/drain cap layer disposed on and in direct contact with the source/drain contact;
• a second sealing layer disposed over and in contact with the source/drain cap layer;
• a source/drain contact via extending through the second sealing layer to couple to the source/drain cap layer, sidewalls of the source/drain contact via being in direct contact with the second sealing layer;
• a spacer extending along a sidewall of the gate structure and a sidewall of the gate cap layer;
• a liner extending along a sidewall of the source/drain contact and a sidewall of the source/drain cap layer;
• an air gap sandwiched between the spacer and the liner;
• and
• a plug feature over the air gap between the spacer and the liner,
• wherein the source/drain contact comprises cobalt,
• wherein the gate structure and the source/drain contact are separated by the spacer, the air gap and the liner,
• wherein the gate contact via and the source/drain contact via are separated by the spacer, the air gap, the first sealing layer, the second sealing layer, and the liner along the direction,
• wherein a top surface of the plug feature and a top surface of the gate contact via are coplanar.

A semiconductor device, comprising:

• a fin extending from a substrate, the fin comprising a channel region and a source/drain region adjacent to the channel region, the fin extending lengthwise along a direction;
• a gate structure over the channel region;
• a silicide layer disposed over the source/drain region;
• a source/drain contact over and in contact with the silicide layer;
• a first dielectric layer disposed directly over the gate structure and the source/drain contact;
• a gate contact via extending through the first dielectric layer and electrically coupled to the gate structure;
• a source/drain contact via extending through the first dielectric layer and electrically coupled to the source/drain contact,
• a spacer extending along a sidewall of the gate structure and a first sidewall of the first dielectric layer;
• a liner extending along a sidewall of the source/drain contact and a second sidewall of the first dielectric layer;
• and
• an air gap sandwiched between the spacer and the liner,
• wherein the silicide layer comprises cobalt silicide, nickel silicide, or titanium silicide,
• wherein the source/drain contact comprises cobalt,
• wherein the gate structure and the source/drain contact are separated by the spacer, the air gap and the liner,
• wherein the gate contact via and the source/drain contact via are separated by the spacer, the air gap, the liner, and a portion of the first dielectric layer along the direction.