Liner for a bi-layer gate helmet and the fabrication thereof

1. A semiconductor device, comprising:

a semiconductor layer;

a gate structure disposed over the semiconductor layer;

an interlayer dielectric (ILD) layer;

a spacer disposed between the gate structure and the ILD layer, wherein a height of the spacer is greater than a height of the gate structure but less than a height of the ILD layer; and

a liner disposed on the gate structure and on the spacer and on a portion of a sidewall of the ILD layer, wherein the spacer and the liner have different material compositions;

wherein:

the gate structure is disposed on a sidewall of a first portion of the spacer; and

the liner is disposed on a sidewall of a second portion of the spacer, wherein the second portion is disposed above the first portion.

2. The semiconductor device of claim 1 , wherein the liner has a greater dielectric constant than the spacer.

3. The semiconductor device of claim 2 , wherein a dielectric constant of the liner is greater than about 4.

4. The semiconductor device of claim 1 , wherein the liner is further disposed on a top surface of the spacer.

5. The semiconductor device of claim 1 , further comprising: a dielectric structure disposed over the liner, wherein the dielectric structure contains a dielectric material having a dielectric constant greater than about 4, and wherein the dielectric structure has a T-shaped profile in a cross-sectional view.

6. The semiconductor device of claim 5 , wherein:

the dielectric structure includes a first portion and a second portion disposed over the first portion; and

a dielectric constant of the second portion is greater than a dielectric constant of the first portion.

7. The semiconductor device of claim 6 , wherein the dielectric structure further includes a third portion disposed between the first portion and the second portion, and wherein a dielectric constant of the third portion is smaller than the dielectric constant of the second portion but greater than the dielectric constant of the first portion.

8. The semiconductor device of claim 6 , wherein the dielectric structure further includes a third portion disposed between the first portion and the second portion, and wherein a dielectric constant of the third portion is smaller than the dielectric constant of the second portion but greater than the dielectric constant of the first portion.

9. The semiconductor device of claim 5 , wherein the dielectric structure contains zirconium oxide or yttrium silicon oxide.

10. A semiconductor device, comprising:

a semiconductor layer;

a gate structure disposed over the semiconductor layer;

a spacer disposed on a sidewall of the gate structure;

an interlayer dielectric (ILD) disposed adjacent to the spacer, wherein the spacer is disposed between the ILD and the gate structure; and

a dielectric structure disposed over the gate structure;

wherein:

the dielectric structure includes a first portion, a second portion disposed over the first portion, and a third portion disposed between the first portion and the second portion;

a first dielectric constant of the first portion is smaller than a second dielectric constant of the second portion;

a third dielectric constant of the third portion is smaller than the second dielectric constant but greater than the first dielectric constant; and

the second dielectric constant is greater than about 4.

11. The semiconductor device of claim 10 , wherein the dielectric structure has a cross-sectional profile that resembles a letter T.

12. The semiconductor device of claim 10 , wherein a portion of the dielectric structure is disposed over an upper surface of the spacer.

13. The semiconductor device of claim 10 , wherein the first dielectric constant is smaller than about 4.

14. The semiconductor device of claim 10 , further comprising: a liner having a dielectric constant greater than about 4, wherein the dielectric structure is disposed over the liner, and wherein the gate structure and the spacer are disposed under the liner.

15. The semiconductor device of claim 14 , wherein a portion of the liner is disposed between a sidewall of a portion of the ILD and a sidewall of a portion of the dielectric structure.

16. The semiconductor device of claim 10 , wherein the dielectric structure contains zirconium oxide or yttrium silicon oxide.

17. A semiconductor device, comprising:

a semiconductor layer;

a gate structure disposed over the semiconductor layer;

an interlayer dielectric (ILD) layer;

a spacer disposed between the ILD layer and the gate structure, the spacer including a lower portion and an upper portion, wherein a height of the spacer is greater than a height of the gate structure but less than a height of the ILD layer, and wherein the gate structure is disposed on a sidewall of the lower portion of the spacer;

a liner disposed on the gate structure, on a portion of a sidewall of the ILD layer, and on a sidewall and an upper surface of the upper portion of the spacer, wherein the spacer has a lower dielectric constant than the liner; and

a dielectric structure disposed over the liner, wherein the dielectric structure has a T-shaped profile in a cross-sectional view and contains a dielectric material having a dielectric constant greater than about 4, wherein the dielectric structure includes a first portion and a second portion disposed over the first portion, and wherein a dielectric constant of the second portion is greater than a dielectric constant of the first portion.

18. The semiconductor device of claim 17 , wherein a dielectric constant of the liner is greater than about 4.

19. The semiconductor device of claim 17 , wherein the dielectric structure further includes a third portion disposed between the first portion and the second portion, and wherein the third portion has a greater dielectric constant than the first portion but a smaller dielectric constant than the second portion.

20. The semiconductor device of claim 17 , wherein the dielectric structure contains zirconium oxide or yttrium silicon oxide.