Semiconductor device and method for fabricating the same

Abstract

A semiconductor device includes a gate structure, two recesses, and two epitaxial structures. The gate structure is disposed on a substrate, wherein a surface of the substrate defines a normal direction. The two recesses are disposed in the substrate and located on both sides of the gate structure. The epitaxial structures are respectively disposed in the two recesses, wherein each epitaxial structure includes a first epitaxial layer and a second epitaxial layer arranged from bottom to top along the normal direction, and the first epitaxial layer and the second epitaxial layer have a first gap in the normal direction.

Claims

1. A semiconductor device comprising: a gate structure disposed on a substrate, wherein a surface of the substrate defines a normal direction; two grooves disposed in the substrate and located on both sides of the gate structure; two epitaxial structures respectively disposed in the two grooves, wherein the two epitaxial structures respectively include a first epitaxial layer and a second epitaxial layer arranged from bottom to top along the normal direction, and the first epitaxial layer and the second epitaxial layer have a first gap in the normal direction; and two contact structures respectively disposed on the two epitaxial structures, wherein a portion of the two contact structures respectively fills the first gap of the two epitaxial structures.

2. The semiconductor device as described in claim 1, wherein the substrate includes a fin structure, the gate structure is disposed on the fin structure, and the two grooves are disposed in the fin structure.

3. The semiconductor device as described in claim 1, wherein no other epitaxial layer is disposed between the first epitaxial layer and the second epitaxial layer.

4. The semiconductor element as claimed in claim 1, wherein the first gap extends along a horizontal direction perpendicular to the normal direction, and the first gap has two openings opposite to each other in the horizontal direction.

5. The semiconductor element as described in claim 4, wherein the first gap has an intermediate section located between the two openings, the first gap has a first height in the intermediate section parallel to the normal direction, the first gap has a second height in one of the two openings parallel to the normal direction, and the first height is less than the second height.

6. The semiconductor element as claimed in claim 1, wherein a portion of one of the two contact structures does not completely fill the first gap of one of the two epitaxial structures.

7. The semiconductor element as claimed in claim 6, wherein one of the epitaxial structures further includes a sub-gap disposed in the portion of one of the contact structures.

8. The semiconductor device as described in claim 1, wherein the two epitaxial structures further include a third epitaxial layer disposed above the second epitaxial layer along the normal direction, and the second epitaxial layer and the third epitaxial layer have a second gap in the normal direction.

9. The semiconductor device as described in claim 1, wherein the materials of the first epitaxial layer and the second epitaxial layer comprise silicon germanium, and the germanium concentration in the first epitaxial layer and the second epitaxial layer is the same.

10. The semiconductor device as described in claim 1, wherein the materials of the first epitaxial layer and the second epitaxial layer comprise silicon phosphorus, and the phosphorus concentration in the first epitaxial layer and the second epitaxial layer is the same.

11. The semiconductor element as claimed in claim 1, wherein in one of the two grooves, the first epitaxial layer directly contacts the bottom surface of the groove, and the top edge of the first epitaxial layer in the normal direction is lower than the top edge of the groove.

12. A method of fabricating a semiconductor device, comprising: forming a gate structure on a substrate, wherein a surface of the substrate defines a normal direction; forming two grooves in the substrate and located on both sides of the gate structure; forming two epitaxial structures respectively in the two grooves, wherein the two epitaxial structures respectively include a first epitaxial layer and a second epitaxial layer arranged from bottom to top along the normal direction, and the first epitaxial layer and the second epitaxial layer have a first gap in the normal direction; and forming two contact structures respectively disposed on the two epitaxial structures, wherein a portion of the two contact structures respectively fills the first gap of the two epitaxial structures.

13. The method described in claim 12, wherein the substrate includes a fin-like structure, the gate structure is disposed on the fin-like structure, and the two grooves are disposed in the fin-like structure.

14. The method as described in claim 12, wherein forming the dual epitaxial structure comprises: The first epitaxial layer, a sacrificial layer, and the second epitaxial layer are sequentially formed in the two grooves, respectively; And remove the sacrificial layer to form the first gap.

15. The method described in claim 14, wherein the material of the sacrificial layer comprises silicon germanium, the materials of the first epitaxial layer and the second epitaxial layer comprise silicon germanium, and the germanium concentration of the sacrificial layer is higher than the germanium concentration of the first epitaxial layer and the second epitaxial layer.

16. The method described in claim 14, wherein the material of the sacrificial layer comprises silicon germanium, and the materials of the first epitaxial layer and the second epitaxial layer comprise silicon phosphorus.

17. The method of claim 12, wherein the first gap extends along a horizontal direction perpendicular to the normal direction, and the first gap has two openings opposite to each other in the horizontal direction.

18. The method of claim 17, wherein the first gap has an intermediate section located between the two openings, the first gap has a first height in the intermediate section parallel to the normal direction, the first gap has a second height in one of the two openings parallel to the normal direction, and the first height is less than the second height.

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