Field effect transistor with negative capacitance dieletric structures

1. A method of fabricating a semiconductor device, the method comprising:

forming a fin structure with a fin base portion and a fin top portion on a substrate;

forming a spacer structure in a first region of the fin top portion, wherein the spacer structure comprises a first negative capacitance (NC) dielectric layer comprising an NC dielectric material, a non-NC dielectric structure and an air gap within the first NC dielectric layer; and

forming a gate structure on a second region of the fin top portion,

wherein the gate structure comprises a gate dielectric layer with a second NC dielectric material different from the first NC dielectric material.

2. The method of claim 1 , wherein the forming the spacer structure comprises:

forming a recessed region in the first region of the fin top portion; and

depositing a layer of the first NC dielectric material in the recessed region.

3. The method of claim 2 , wherein the depositing the layer of the first NC dielectric material comprises:

depositing a layer of high-k dielectric material;

doping the layer of high-k dielectric material with a conductive material.

4. The method of claim 1 , wherein the forming the spacer structure comprises:

forming a recessed region in the first region of the fin top portion;

depositing a layer of the first NC dielectric material to line sides of the recessed region; and

forming the non-NC dielectric structure and the air gap on the layer of the first NC dielectric material within the recessed region.

5. The method of claim 4 , wherein the forming the non-NC dielectric structure and the air gap comprises:

depositing a layer of non-NC dielectric material to substantially fill an area of the recessed region lined with the layer of the first NC dielectric material;

etching back the layer of non-NC dielectric material; and

epitaxially growing a source/drain region on the fin base portion and the first region of the fin top portion, wherein the source/drain region covers an opening of the recessed region and forms the air gap between the source/drain region and the etched backed layer of non-NC dielectric material.

6. The method of claim 1 , wherein the forming the gate structure comprises etching a fin portion in the second region of the fin top portion, and

wherein the fin portion is adjacent to the spacer structure.

7. The method of claim 1 , wherein the forming the gate structure comprises depositing a layer of the second NC dielectric layer on the second region of the fin top portion, and

wherein the second region is adjacent to the spacer structure.

8. The method of claim 7 , wherein the depositing the layer of the second NC dielectric layer comprises:

depositing a layer of hafnium oxide; and

doping the layer of hafnium oxide with a metal.

9. The method of claim 1 , wherein the forming the gate structure comprises depositing the layer of the second NC dielectric layer wrapped around the second region of the fin top portion.

10. The method of claim 1 , wherein the forming the gate structure comprises depositing a work function metal layer wrapped around the second region of the fin top portion.

11. A method of fabricating a semiconductor device, the method comprising:

forming a fin structure with a stacked fin portion and a fin base portion on a substrate, wherein the stacked fin portion is epitaxially grown on the fin base portion;

forming an epitaxial source/drain region on the fin structure;

forming a first negative capacitance (NC) dielectric structure in a first region of the stacked fin portion, wherein the first NC dielectric structure comprises a first dielectric layer with a first NC material;

forming gate structures on a second region of the stacked fin portion, wherein the gate structures each comprises a second dielectric layer with the first NC material;

forming a source/drain contact structure on the epitaxial source/drain region; and

forming a second NC dielectric structure between the source/drain contact structure and the gate structures, wherein the second NC dielectric structure comprises a third dielectric layer with the first NC material.

12. The method of claim 11 , wherein the forming the first NC dielectric structure comprises:

forming a recessed region in the first region of the stacked fin portion;

depositing a layer of the first NC material within the recessed region; and

forming a dielectric structure on the layer of the first NC material within the recessed region.

13. The method of claim 11 , wherein the forming the second NC dielectric structure comprises:

forming a trench on the epitaxial source/drain region between the gate structures;

depositing a layer of the first NC material along sides of the trench;

depositing a nitride layer on the layer of the first NC material; and

etching back the nitride layer.

14. The method of claim 13 , wherein the depositing the layer of the first NC material comprises:

depositing a layer of high-k dielectric material; and

doping the layer of high-k dielectric material with a conductive material.

15. The method of claim 13 , wherein the depositing the layer of the first NC material comprises:

depositing a layer of hafnium oxide;

doping the layer of hafnium oxide with a metal; and

annealing the doped hafnium oxide.

16. A method of fabricating a semiconductor device, the method comprising:

forming a fin structure with a fin base portion and a fin top portion on a substrate;

forming a spacer structure in a first region of the fin top portion, wherein the spacer structure comprises a negative capacitance (NC) dielectric layer comprising an NC dielectric material, a non-NC dielectric structure, and an air gap;

forming a source/drain region on the fin base portion and in contact with the fin top portion, wherein the source/drain region, the NC dielectric layer, and the non-NC dielectric structure enclose the air gap; and

forming a gate structure on a second region of the fin top portion, wherein the gate structure comprises a gate dielectric layer having the NC dielectric material.

17. The method of claim 16 , wherein the forming the spacer structure comprises:

forming a recessed region in the first region of the fin top portion;

depositing a layer of the NC dielectric material in the recessed region;

depositing a layer of non-NC dielectric material to substantially fill the recessed region;

etching back the layer of non-NC dielectric material to form the non-NC dielectric structure; and

etching back the layer of NC dielectric material to form the NC dielectric layer.

18. The method of claim 17 , wherein the depositing the layer of the NC dielectric material comprises:

depositing a layer of high-k dielectric material; and

doping the layer of high-k dielectric material with a conductive material.

19. The method of claim 17 , wherein the depositing the layer of the NC material comprises:

depositing a layer of hafnium oxide;

doping the layer of hafnium oxide with a metal; and

annealing the doped layer of hafnium oxide.

20. The method of claim 16 , wherein the forming the gate structure comprises:

etching a fin portion in the second region of the fin top portion, wherein the fin portion is adjacent to the spacer structure;

depositing a layer of the NC dielectric material wrapped around the second region of the fin top portion; and

depositing a work function metal layer on the gate dielectric layer.