Patent ID: 7737506

Claim:
A semiconductor device comprising: a first insulating film formed over an insulating surface, the first insulating film having an opening portion; a second insulating film over the insulating surface and in the opening portion of the first insulating film; a crystalline semiconductor film formed over the insulating surface and in the opening portion of the first insulating film; a third insulating film over and in contact with the first insulating film, the second insulating film and the crystalline semiconductor film; and a gate electrode over the first insulating film, the second insulating film and the crystalline semiconductor film with the third insulating film therebetween wherein the gate electrode overlaps with the first insulating film, the second insulating film and the crystalline semiconductor film, wherein a part of the crystalline semiconductor film is located between the first and the second insulating films; wherein the crystalline semiconductor film comprises a first channel forming region extended to a first direction, wherein the gate electrode is located over the first channel forming region, and wherein the opening portion is extended in the first direction.