Air Spacer and Method of Forming Same

A method of forming a semiconductor device, the method comprising:

• forming a first gate structure and a second gate structure over a substrate;
• depositing a first dielectric layer over and extending from the first gate structure to the second gate structure;
• oxidizing an exposed surface of the first dielectric layer to form a first oxygen-containing layer;
• depositing a second oxygen-containing layer over the first oxygen-containing layer;
• etching the first dielectric layer, the first oxygen-containing layer, and the second oxygen-containing layer to expose the substrate;
• depositing a second dielectric layer over the second oxygen-containing layer, the second dielectric layer extending over and between the first gate structure and the second gate structure;
• and
• etching the first oxygen-containing layer and the second oxygen-containing layer to form an air gap, the air gap being partially bounded by the first dielectric layer and the second dielectric layer.

A method of forming a semiconductor device, the method comprising:

• forming semiconductor fins over a substrate, the semiconductor fins comprising a first semiconductor fin and a second semiconductor fin;
• forming an isolation region over the substrate and between the first semiconductor fin and the second semiconductor fin;
• forming a dummy gate structure over the semiconductor fins;
• forming a first spacer layer over the dummy gate structure and the semiconductor fins;
• forming a second spacer layer over the first spacer layer;
• performing an etch process to form a first recess in the first semiconductor fin and a second recess in the second semiconductor fin;
• forming a first epitaxial region in the first recess and a second epitaxial region in the second recess;
• forming a third spacer layer over the first epitaxial region and the second epitaxial region;
• performing a planarization process to level the dummy gate structure with the first spacer layer, the second spacer layer, and the third spacer layer;
• etching the second spacer layer to form a third recess below level top surfaces of the first spacer layer and the third spacer layer;
• and
• forming a refill layer in an upper portion of the third recess to bound an air gap below a lower surface of the refill layer.