Transistor with airgap spacer and tight gate pitch

1. A semiconductor structure comprising:

a functional gate structure located on a channel region of a semiconductor material portion, wherein a source/drain (S/D) region is located at each end of the channel region;

a contact structure located laterally adjacent to, and on both sides of, the functional gate structure, wherein the contact structure contacts a surface of the source/drain region; and

an airgap spacer located between the functional gate structure and the contact structure, wherein the airgap spacer is L-shaped and is sandwiched between a lower dielectric material spacer that is L-shaped and an upper dielectric material spacer, wherein the lower dielectric material spacer has a horizontal portion that directly contacts a lower sidewall portion of the contact structure, and the upper dielectric material spacer has a vertical portion that directly contacts an upper sidewall portion of the contact structure, and wherein the contact structure passes through the horizontal portion of the lower dielectric spacer and a horizontal portion of the airgap spacer.

2. The semiconductor structure of claim 1 , wherein the upper dielectric material spacer is also L-shaped, and the contact structure passes through a horizontal portion of the upper dielectric material spacer.

3. The semiconductor structure of claim 1 , wherein the horizontal portion of the lower dielectric material spacer is adjacent to a bottom portion of the functional gate structure and extends onto a portion of the S/D region.

4. The semiconductor structure of claim 1 , wherein the airgap spacer is sealed at a first end with a first airgap spacer cap and at a second end with a second airgap spacer cap.

5. The semiconductor structure of claim 4 , wherein the first airgap spacer cap is located above an isolation structure that is located laterally adjacent to the semiconductor material portion, and the second airgap spacer cap is located at a top of the airgap spacer.

6. The semiconductor structure of claim 1 , wherein a vertical portion of the lower dielectric material spacer is spaced apart from the functional gate structure by a dielectric material structure that is I-shaped and is composed of a dielectric material having a low dielectric constant.

7. The semiconductor structure of claim 1 , further comprising a gate cap located on the functional gate structure and a dielectric cap located on the contact structure.

8. The semiconductor structure of claim 1 , further comprising an interlayer dielectric material located laterally adjacent to the contact structure.

9. The semiconductor structure of claim 1 , wherein the semiconductor material portion is located on a substrate, and the substrate is composed of a semiconductor material or an insulator material.