Patent ID: 8242494
Filing Date: 2012-08-14
Classification: H01L

Abstract:
1. A method for manufacturing a semiconductor device, comprising: forming a gate electrode layer over a substrate having an insulating surface; forming a gate insulating layer over the gate electrode layer; performing reverse sputtering treatment on the gate insulating layer in an atmosphere comprising an argon gas; forming an oxide semiconductor film over the gate electrode layer after performing reverse sputtering treatment on the gate insulating layer; forming a conductive film over the gate electrode layer; forming a first mask layer over the gate insulating layer, the oxide semiconductor film, and the conductive film; forming an oxide semiconductor layer and a conductive layer by etching the oxide semiconductor film and the conductive film with the use of the first mask layer in a first etching step; forming a second mask layer by ashing the first mask layer; and forming an oxide semiconductor layer having a depression, a source electrode layer, and a drain electrode layer by etching the oxide semiconductor layer and the conductive layer with the use of the second mask layer in a second etching step, wherein the first mask layer is formed using a light-exposure mask, wherein wet etching in which an etchant is used is employed in the first etching step, wherein dry etching in which an etching gas is used is employed in the second etching step, and wherein the oxide semiconductor layer having the depression includes a region with a smaller thickness than a region overlapping with the source electrode layer or the drain electrode layer.