Patent ID: 8999751
Filing Date: 2015-04-07
Classification: H01L

Abstract:
1. A method for manufacturing a semiconductor device, comprising the steps of: forming a first conductive layer over a substrate; forming a first insulating layer over the first conductive layer; forming an oxide semiconductor layer over the first insulating layer, the oxide semiconductor layer overlapping the first conductive layer; heating the oxide semiconductor layer to increase crystallinity of the oxide semiconductor layer; forming a second conductive layer and a third conductive layer which are in contact with the oxide semiconductor layer; forming a second insulating layer over the oxide semiconductor layer, the second conductive layer, and the third conductive layer; and forming a fourth conductive layer over the second insulating layer, the fourth conductive layer overlapping a part of the oxide semiconductor layer, wherein the fourth conductive layer overlaps the second conductive layer and the third conductive layer, wherein the oxide semiconductor layer comprises a first region and a second region, the first region being located over the second region, wherein the first region comprises a crystal, and a c-axis of the crystal is substantially perpendicular to the second insulating layer, wherein the second region has a lower crystallinity than the first region, and wherein all the metal elements included in the first region are included in the second region, and all the metal elements included in the second region are included in the first region.