Semiconductor device including oxide semiconductor layer

摘要

The electrical characteristics of a transistor including an oxide semiconductor layer are varied by influence of an insulating film in contact with the oxide semiconductor layer, that is, by an interface state between the oxide semiconductor layer and the insulating film. A first oxide semiconductor layer S1, a second oxide semiconductor layer S2, and a third oxide semiconductor layer S3 are sequentially stacked, so that the oxide semiconductor layer through which carriers flow is separated from the gate insulating film containing silicon. The thickness of the first oxide semiconductor layer S1 is preferably smaller than those of the second oxide semiconductor layer S2 and the third oxide semiconductor layer S3, and is less than or equal to 10 nm, preferably less than or equal to 5 nm.

主权项

1. A semiconductor device comprising:
a first insulating layer over an insulating surface; a first oxide semiconductor layer over the first insulating layer; a second oxide semiconductor layer over the first oxide semiconductor layer; a third oxide semiconductor layer over the second oxide semiconductor layer; a first electrode layer and a second electrode layer over the third oxide semiconductor layer; and a second insulating layer over the third oxide semiconductor layer, wherein the first oxide semiconductor layer, the second oxide semiconductor layer and the third oxide semiconductor layer comprise same constituent elements, wherein a composition of the second oxide semiconductor layer is different from a composition of the first oxide semiconductor layer and a composition of the third oxide semiconductor layer, and wherein an energy level of a bottom of a conductive band of the first oxide semiconductor layer is continuously changed to an energy level of a bottom of a conductive band of the second oxide semiconductor layer at an interface between the second oxide semiconductor layer and the first oxide semiconductor layer.