Abstract: A method of fabricating a semiconductor device is provided wherein a first semiconductor substrate is prepared with a first insulating film formed over a first main surface of the first semiconductor substrate, s semiconductor film of n-type conductivity formed over the first insulating film, and a second insulating film formed over the semiconductor film so as to cover the first main surface. A second semiconductor substrate is also prepared with a third insulating film formed over the second semiconductor substrate. Next, the second insulating film and third insulating films are bonded together by thermal processing to join the first semiconductor substrate and the second semiconductor substrate. A portion of a second main surface of said first semiconductor substrate, opposite to said first main surface of the first semiconductor substrate is then removed to expose a portion of the first semiconductor substrate, thereby providing a semiconductor layer.