FinFET structure with airgap and method of forming the same

1. A device comprising:

a fin structure disposed on a substrate;

a gate structure disposed on the fin structure, the gate structure including:

a gate dielectric layer;

a gate electrode disposed on the gate dielectric layer; and

a protective layer disposed on the gate electrode and interfacing with a first portion of a side surface of the gate dielectric layer, the side surface of the gate dielectric facing the gate electrode and a second portion of the side surface of the gate electrode being exposed to a first air gap, the first air gap extending between the side surface of the gate dielectric and the second portion of the side surface of the gate electrode.

2. The device of claim 1 , wherein a bottom portion of the gate electrode interfaces with the gate dielectric layer.

3. The device of claim 1 , further comprising:

an interlayer dielectric layer disposed on the gate structure;

a source/drain feature disposed on the fin structure; and

a second air gap extending from the source/drain feature to the interlayer dielectric layer.

4. The device of claim 1 , wherein the gate dielectric layer extends to a greater height above the substrate than the gate electrode.

5. The device of claim 1 , further comprising:

an etch stop layer disposed on the protective layer; and

a contact feature extending through the etch stop layer and the protective layer such that the contact feature interfaced with the gate electrode.

6. The device of claim 1 , wherein the gate dielectric layer and the protective layer interface with the etch stop layer.

7. The device of claim 1 , wherein the gate dielectric has a u-shaped cross-sectional profile.

8. The device of claim 1 , wherein the first air gap extends an entire length of the gate electrode.

9. A device comprising:

a fin structure disposed on a substrate;

a gate structure disposed on the fin structure, the gate structure including:

a gate dielectric layer;

a gate electrode disposed on the gate dielectric layer; and

a first air gap extending from the gate dielectric layer to the gate electrode such that the gate dielectric layer and the gate electrode are exposed to the first air gap;

a source/drain feature disposed on the fin structure;

a contact feature interfacing with the source/drain feature; and

a second air gap extending from the contact feature to the source/drain feature such that the contact feature and the source/drain feature are exposed to the second air gap.

10. The device of claim 9 , further comprising a first protective layer disposed on the contact features and exposed to the second air gap.

11. The device of claim 10 , wherein the first protective layer includes a bottom surface facing the substrate, the bottom surface of the first protective layer being exposed to the second air gap.

12. The device of claim 9 , further comprising a sidewall spacer disposed on the gate structure, and

wherein the gate electrode is recessed relative to a top surface of the sidewall spacer.

13. The device of claim 12 , wherein the sidewall spacer interfaces with the gate dielectric layer and is not exposed to the first air gap.

14. The device of claim 9 , wherein the source/drain feature includes a top surface facing away from the substrate, and

wherein at least a portion of the top surface of the source/drain feature is exposed to the second air gap.

15. The device of claim 9 , wherein the gate dielectric layer includes a high-k dielectric material and the gate electrode includes a metal material.

16. A method comprising:

forming a first trench in an interlayer dielectric layer disposed on a substrate;

forming a gate dielectric layer in the first trench;

forming a first layer on the gate dielectric layer within the first trench;

removing a first portion of the first layer to expose a portion of the gate dielectric layer, wherein a second portion of the first layer remains disposed within the first trench after the removing of the first portion of the first layer;

forming a gate electrode within the first trench on the second portion of the first layer; and

removing the second portion of the first layer to form a first air gap between the gate electrode and the gate dielectric layer.

17. The method of claim 16 , further comprising:

forming a source/drain feature on the substrate;

forming a second trench in the interlayer dielectric layer to expose the source/drain feature;

forming a second layer on the source/drain feature within the second trench;

removing a first portion of the second layer to expose a portion of the source/drain feature, wherein a second portion of the second layer remains disposed within the second trench after the removing of the first portion of the second layer;

forming a contact feature within the second trench on the second portion of the second layer; and

removing the second portion of the second layer to form a second air gap between the contact feature and the interlayer dielectric layer.

18. The method of claim 17 , wherein the removing of the second portion of the second layer to form the occurs during the same removal process as the removing of the second portion of the first layer to form the first air gap.

19. The method of claim 16 , further comprising recessing the gate electrode prior to removing the second portion of the first layer to form the first air gap.

20. The method of claim 16 , further comprising forming a protective layer directly on the recessed gate electrode, and

wherein the protective layer interfaces with the gate electrode and the gate dielectric layer after forming the protective layer directly on the recessed gate electrode.