Patent ID: 8394671
Filing Date: 2013-03-12
Classification: H01L

Abstract:
1. A method for manufacturing a semiconductor device comprising the steps of: forming a first oxide semiconductor film over an insulating layer; forming a second oxide semiconductor film over the first oxide semiconductor film; performing a first heat treatment on the first oxide semiconductor film and the second oxide semiconductor film and then cooling the first oxide semiconductor film and the second oxide semiconductor film in an atmosphere containing oxygen; etching the first oxide semiconductor film and the second oxide semiconductor film after the cooling step to form a first oxide semiconductor layer from the first oxide semiconductor film and a second oxide semiconductor layer from the second oxide semiconductor film; forming a conductive film over the first oxide semiconductor layer and the second oxide semiconductor layer; etching the second oxide semiconductor layer and the conductive film to form a source region, a drain region, a source electrode layer, and a drain electrode layer; and forming an oxide insulating film in contact with part of the first oxide semiconductor layer.