V-shape recess profile for embedded source/drain epitaxy

1. A semiconductor device, comprising:

a semiconductor layer;

an isolation structure formed in the semiconductor layer; and

an epi-layer component formed on the semiconductor layer;

wherein:

the epi-layer component includes at least one first portion that extends into the semiconductor layer and a second portion that is disposed above the at least one first portion;

a maximum lateral dimension of the second portion occurs at a region of the second portion that is located above the isolation structure;

a lateral dimension of the at least one first portion of the epi-layer component decreases as the at least one first portion extends further into the semiconductor layer; and

a substantial majority of a side surface of the at least one first portion of the epi-layer component is free of being in direct contact with the isolation structure.

2. The semiconductor device of claim 1 , wherein the at least one first portion of the epi-layer component has a cross-sectional profile that resembles a letter V.

3. The semiconductor device of claim 2 , wherein the epi-layer component defines an upwardly-facing angle that is less than about 120 degrees.

4. The semiconductor device of claim 1 , wherein:

the at least one first portion of the epi-layer component has a depth and a width; and

the depth is greater than about ½ of the width.

5. The semiconductor device of claim 1 , wherein the epi-layer component includes a source/drain of a FinFET transistor.

6. The semiconductor device of claim 1 , further comprising a silicon capping layer or a silicon germanium capping layer disposed over the second portion.

7. The semiconductor device of claim 1 , wherein:

the at least one first portion includes a plurality of first portions; and

the second portion is disposed above the plurality of first portions.

8. The semiconductor device of claim 7 , wherein:

the plurality of first portions are separated from one another by a plurality of dielectric components disposed in the semiconductor layer; and

a respective air gap is disposed above each dielectric component and below the second portion of the epi-layer component.

9. The semiconductor device of claim 6 , wherein a middle part of the second portion of the epi-layer component protrudes laterally outward.

10. A semiconductor device, comprising:

a semiconductor base;

a dielectric isolation structure formed in the semiconductor base; and

a source/drain of a FinFET transistor formed on the semiconductor base;

wherein:

at least one bottom segment of the source/drain is embedded into the semiconductor base;

the at least one bottom segment of the source/drain has a V-shaped cross-sectional profile;

the at least one bottom segment of the source/drain is separated from the dielectric isolation structure by portions of the semiconductor base;

the at least one bottom segment of the source/drain has a vertical dimension and a lateral dimension; and

the vertical dimension is greater than about ½ of the lateral dimension.

11. The semiconductor device of claim 10 , wherein the V-shaped cross-sectional profile corresponds to an angle that is less than about 120 degrees.

12. The semiconductor device of claim 10 , wherein:

the at least one bottom segment includes a plurality of bottom segments that each have the V-shaped cross-sectional profile; and

a remaining segment of the source/drain is disposed over the plurality of the bottom segments and over the semiconductor base.

13. The semiconductor device of claim 12 , wherein:

a plurality of dielectric elements is located in the semiconductor base;

the dielectric elements are each located between a different pair of the bottom segments of the source/drain, respectively; and

a plurality of air gaps are trapped between the remaining segment of the source/drain and the dielectric elements.

14. The semiconductor device of claim 10 , wherein a remaining segment of the source/drain that is disposed above the bottom segment, the remaining segment having a cross-sectional profile that resembles a diamond or a football.

15. A method of fabricating a semiconductor device, comprising:

providing a FinFET device, wherein the FinFET device includes: a dielectric isolation structure formed in a semiconductor layer, a semiconductor fin structure that protrudes out of the semiconductor layer, and a gate that is formed over and wraps around the semiconductor fin structure;

forming a recess in the semiconductor fin structure, the recess extending into the semiconductor layer and having a cross-sectional profile that resembles a letter V, such that a substantial majority of a side surface of the recess is not in direct contact with the dielectric isolation structure;

growing a source/drain of the FinFET device in the recess using an epitaxial process, wherein the source/drain fills the recess and protrudes out of the recess; and

forming a silicon capping layer or a silicon germanium capping layer on the source/drain.

16. The method of claim 15 , wherein the recess is formed such that it defines an upwardly-facing angle that is less than about 120 degrees.

17. The method of claim 15 , wherein the recess is formed such that a depth of the recess is greater than about ½ of a width of the recess.

18. The method of claim 15 , wherein the forming the recess comprises an etching process that includes a dry etching component.

19. The method of claim 15 , wherein the growing the source/drain is performed such that a portion of the source/drain that protrudes out of the recesses traps an air gap underneath.

20. The semiconductor device of claim 10 , wherein a region of the source/drain having a maximum lateral dimension is located above an upper surface of the dielectric isolation structure.