Heterogeneous semiconductor device substrates with high quality epitaxy

1. A method of manufacturing a semiconductor structure, the method comprising:

etching a semiconductor substrate having a top surface extending along a (001) crystal plane, such that a majority of a top surface of the etched semiconductor substrate extends along {111} crystal planes;

forming a first epitaxial layer in contact with the top surface of the etched semiconductor substrate;

forming a second epitaxial layer on the first epitaxial layer, wherein a bottommost surface of the second epitaxial layer is higher than a topmost surface of the semiconductor substrate, and the bottommost surface of the second epitaxial layer is substantially planar; and

forming an isolation region in the second epitaxial layer and spaced apart from the first epitaxial layer.

2. The method of claim 1 , further comprising:

forming a mask layer on the semiconductor substrate; and

patterning the mask layer to form a plurality of dot-shaped mask portions arranged on the semiconductor substrate in a spaced apart manner, wherein etching the semiconductor substrate is performed after patterning the mask layer.

3. The method of claim 2 , wherein etching the semiconductor substrate is performed such that the patterned mask layer is removed.

4. The method of claim 2 , wherein one of the dot-shaped mask portions has a diameter substantially equal to a spacing between the dot-shaped mask portions.

5. The method of claim 2 , wherein the dot-shaped mask portions have substantially equal size.

6. The method of claim 1 , further comprising:

forming a mask layer on the semiconductor substrate; and

etching a plurality of circular holes in the mask layer to expose the semiconductor substrate, wherein etching the semiconductor substrate is performed after etching the circular holes.

7. The method of claim 6 , wherein the circular holes are arranged in a staggered pattern.

8. The method of claim 6 , wherein the circular holes are arranged in non-staggered pattern.

9. The method of claim 1 , wherein etching the semiconductor substrate is performed using at least one of potassium hydroxide (KOH) and tetramethyl-ammonium-hydroxide (TMAH).

10. A method of manufacturing a semiconductor structure, the method comprising:

forming first and second recesses in a semiconductor substrate, wherein the first and second recesses are immediately adjacent to each other, a sidewall of one of the first and second recesses extends along a {111} crystal plane, and the first and second recesses share an edge;

forming a first epitaxial layer in the first and second recesses, wherein a thickness of the first epitaxial layer is greater than a depth of the first recess, and the first epitaxial layer is a single piece of continuous material; and

forming a second epitaxial layer on the first epitaxial layer, such that the second epitaxial layer has a portion directly above the edge shared by the first and second recesses.

11. The method of claim 10 , further comprising:

forming a mask layer on the semiconductor substrate; and

etching the mask layer to form a plurality of dots arranged in rows and columns, wherein the first and second recesses are formed after etching the mask layer.

12. The method of claim 10 , wherein forming the first and second recesses comprises etching the semiconductor substrate, and an etchant used in the etching the semiconductor substrate has a higher etch rate in a (100) crystal plane than in a (111) crystal plane.

13. The method of claim 10 , wherein forming the first and second recesses comprises etching the semiconductor substrate, and an etchant used in the etching the semiconductor substrate has a higher etch rate in a (110) crystal plane than in a (111) crystal plane.

14. The method of claim 10 , further comprising:

forming a transistor on the second epitaxial layer and over the first and second recesses.

15. The method of claim 10 , further comprising forming an isolation region in the second epitaxial layer, wherein a bottom surface of the isolation region is higher than a bottom surface of the second epitaxial layer.

16. A semiconductor structure, comprising:

a substrate;

a first epitaxial layer over the substrate and including a plurality of pyramid protrusions in the substrate, wherein the pyramid protrusions are arranged at least in a first row and a second row, the first and second rows extend in a first direction and are adjacent to each other, the pyramid protrusions have base edges extending in a second direction crossing the first direction, the base edges of the pyramid protrusions in the first row are misaligned with the base edges of the pyramid protrusions in the second row in the second direction;

a second epitaxial layer over the first epitaxial layer; and

an isolation region embedded in the second epitaxial layer.

17. The semiconductor structure of claim 16 , wherein one of the pyramid protrusions has a sidewall extending along a {111} crystal plane.

18. The semiconductor structure of claim 16 , wherein the first epitaxial layer is lattice mismatched to the substrate.

19. The semiconductor structure of claim 16 , wherein the isolation region is spaced apart from the first epitaxial layer.

20. The semiconductor structure of claim 16 , wherein a top surface of the second epitaxial layer is flatter than a bottom surface of the second epitaxial layer.