Patent ID: 9716003
Date: 2017-07-25
CPC Classifications: H01L

Claim:
1. A method of manufacturing a semiconductor device, comprising the steps of: forming a first oxide semiconductor layer containing a single metal element as a constituent element over a substrate by a thermal chemical vapor deposition method; forming a second oxide semiconductor layer containing two or more metal elements as constituent elements by the thermal chemical vapor deposition method and by epitaxial growth using the first oxide semiconductor layer as a seed crystal successively after the first oxide semiconductor layer is formed; and forming an insulating layer over the second oxide semiconductor layer, wherein the second oxide semiconductor layer comprises indium, an element M, and zinc, M being Al, Ti, Ga, Y, Zr, La, Ce, Nd, or Hf, and wherein the second oxide semiconductor layer has a concentration gradient such that, near an interface with the insulating layer, the concentration of element M is lower as the second oxide semiconductor layer is farther from the insulating layer, and near an interface with the first oxide semiconductor layer, the concentration of element M is lower as the second oxide semiconductor layer is farther from the first oxide semiconductor layer.