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 application_number US 201615296027 A description referring to fig1 4 fig1 4 illustrate a method for fabricating substrate of a semiconductor device according to a preferred embodiment of the present invention as shown in fig1 a first silicon layer 12 is provided a dielectric layer 14 is then formed on the first silicon layer 12 and then a second silicon layer 16 is bonded to the dielectric layer 14 to forma silicon on insulator soi structure in this embodiment the dielectric layer 14 is composed of silicon dioxide aluminum oxide or silicon nitride and each one of the first silicon layer 12 and the second silicon layer 16 is preferably composed single crystal silicon preferably both the first silicon layer 12 and the second silicon layer 16 includes a 100 crystalline orientation and a lt 100 gt channel direction before the second silicon layer 16 is bonded to the dielectric layer 14 according to a preferred embodiment of the present invention the second silicon.