Oxide semiconductor layer and semiconductor device

摘要

An object is to provide an oxide semiconductor layer having a novel structure which is preferably used for a semiconductor device. Alternatively, another object is to provide a semiconductor device using an oxide semiconductor layer having the novel structure. An oxide semiconductor layer includes an amorphous region which is mainly amorphous and a crystal region containing crystal grains of In2Ga2ZnO7 in a vicinity of a surface, in which the crystal grains are oriented so that the c-axis is almost vertical with respect to the surface. Alternatively, a semiconductor device uses such an oxide semiconductor layer.

主权项

1. A semiconductor device comprising:
a substrate; a gate electrode layer over the substrate; a gate insulating layer over the gate electrode layer; a first oxide semiconductor layer over the gate insulating layer; a second oxide semiconductor layer over the first oxide semiconductor layer; and a source electrode layer and a drain electrode layer electrically connected to the second oxide semiconductor layer, wherein each of the first oxide semiconductor layer and the second oxide semiconductor layer comprises an oxide semiconductor containing In, Ga, and Zn, wherein the second oxide semiconductor layer includes crystals each containing In, Ga, and Zn as main components, wherein in each of the crystals, a length in a c-axis direction is smaller than a length in an a-axis direction or a b-axis direction, and wherein the crystals are oriented so that c-axes of the crystals are almost vertical with respect to a surface of the second oxide semiconductor layer.