Method for fabricating substrate of semiconductor device including epitaxial layer and silicon layer having same crystalline orientation

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

providing a first silicon layer;

forming a dielectric layer on the first silicon layer;

rotating a second silicon layer by 45 degrees;

bonding the second silicon layer to the dielectric layer so that the second silicon layer and the first silicon layer comprise different channel directions;

removing part of the second silicon layer and part of the dielectric layer to define a first region and a second region on the first silicon layer, wherein the remaining of the second silicon layer and the dielectric layer are on the second region; and

forming an epitaxial layer on the first region of the first silicon layer, wherein the epitaxial layer and the second silicon layer comprise same crystalline orientation.

2. The method of claim 1 , further comprising:

forming a patterned hard mask on the second silicon layer after bonding the second silicon layer to the dielectric layer;

using the patterned hard mask to remove the part of the second silicon layer and the part of the dielectric layer for defining the first region and the second region on the first silicon layer; and

using the patterned hard mask for forming the epitaxial layer in the first region of the first silicon layer.

3. The method of claim 2 , wherein the patterned hard mask comprises silicon nitride.

4. The method of claim 1 , wherein the dielectric layer comprises silicon dioxide, aluminum oxide, or silicon nitride.

5. The method of claim 1 , wherein the epitaxial layer comprises silicon carbide or silicon germanium.

6. The method of claim 1 , wherein the epitaxial layer, the first silicon layer, and the second silicon layer comprise same crystalline orientation.

7. The method of claim 1 , wherein the epitaxial layer and the second silicon layer comprise different channel directions.

8. The method of claim 1 , wherein the epitaxial layer and the first silicon layer comprise same channel direction.

9. The method of claim 1 , further comprising:

removing part of the epitaxial layer and part of the second silicon layer and the dielectric layer for forming a plurality of fin-shaped structures in the first region and the second region;

forming a plurality of gate structures on the fin-shaped structures; and

forming a spacer around each of the gate structures.