Patent ID: 7863117

Claim:
A method of forming a circuit, comprising the steps of: forming a lower semiconductor device having a first active region comprising a semiconductor with a first crystal orientation; forming, separately, an upper semiconductor device having a second active region comprising a semiconductor with a second crystal orientation; and in a separate step after the forming the upper semiconductor device, superimposing the formed upper semiconductor device on the lower semiconductor device, wherein: the forming the lower semiconductor device comprises: forming a first insulating layer on top of a first substrate; forming a seed hole and at least one trench in the first insulating layer; epitaxially growing silicon starting at a bottom of the seed hole, up and out of the seed hole, over a top of the first insulating layer, and down into the at least one trench to form at least one silicon island in the first insulating layer; and polishing to remove the epitaxially grown silicon that extends above the top surface of the first insulating layer; wherein the first active region is comprised in the at least one silicon island and has a same crystal orientation as the first substrate; the forming the upper semiconductor device comprises forming: a second substrate; a second insulating layer on top of the second substrate; and the second active region on top of the second insulating layer; the superimposing comprises forming a bonding layer between a top of the lower semiconductor device and a bottom of the upper semiconductor device, wherein the bonding layer contacts a bottom portion of the second substrate and bonds the upper semiconductor device to the lower semiconductor device; and the first crystal orientation is different from the second crystal orientation.