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

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.