Patent ID: 8916867

Claim:
A semiconductor device comprising: an oxide semiconductor layer on an insulating surface; a gate insulating layer over the oxide semiconductor layer; and a gate electrode over the oxide semiconductor layer with the gate insulating layer provided therebetween, wherein the oxide semiconductor layer has a stacked-layer structure comprising a first oxide semiconductor film including indium and zinc and a second oxide semiconductor film including indium and zinc, wherein the second oxide semiconductor film is sandwiched between the gate insulating layer and the first oxide semiconductor film, wherein a value of a band gap of the first oxide semiconductor film is smaller than a value of a band gap of the second oxide semiconductor film, wherein the first oxide semiconductor film comprises a first non-single-crystal region, wherein the second oxide semiconductor film comprises a second non-single-crystal region, wherein the first non-single-crystal region and the second non-single-crystal region are in contact with each other, and wherein a c-axis of the first non-single-crystal region is in the same direction as a c-axis of the second non-single-crystal region, in a vicinity of an interface between the first non-single-crystal region and the second non-single-crystal region.