Semiconductor device with air-spacer

A semiconductor device, comprising:

• two source/drain (S/D) regions over a substrate;
• a gate stack over the substrate and between the two S/D regions, wherein the gate stack includes a gate dielectric layer and a gate electrode layer;
• a spacer layer along sidewalls of the gate stack;
• an S/D contact metal disposed over and electrically connected to one of the two S/D regions;
• a first dielectric layer interposing the S/D contact metal and the gate stack;
• and
• a second dielectric layer over the first dielectric layer, the spacer layer, and the gate stack, thereby defining a gap, wherein the gap includes air, the gap defined by a first sidewall, a second sidewall opposing the first sidewall, an upper surface and a lower surface, wherein a material of the first sidewall of the gap is different from materials of the upper surface and the lower surface of the gap, and a material of the second sidewall of the gap is different from the materials of the upper surface and the lower surface of the gap, and wherein the lower surface of the gap is coplanar with or higher than an uppermost surface of each of the two S/D regions.

A semiconductor device, comprising:

• two source/drain (S/D) regions over a substrate;
• a gate stack over the substrate and between the two S/D regions in a first direction parallel a top surface of the substrate;
• a spacer layer over sidewalls of the gate stack and having an upper surface substantially coplanar with an upper surface of the gate stack;
• an S/D contact metal disposed over and electrically connected to one of the two S/D regions;
• a first dielectric layer interfacing sidewalls of the S/D contact metal, wherein the first dielectric layer has a first sidewall extending in a direction different than the first direction, the first sidewall aligned with an edge of one of the two S/D regions;
• and
• a gap extending, in the first direction, from the first sidewall of the first dielectric layer to a sidewall of the spacer layer, the sidewall of the spacer layer extending in a direction different than the first direction, wherein a bottom surface of the gap includes a different material than spacer layer and the first dielectric layer, and wherein the gap includes air extending from the first dielectric layer to the spacer layer.