SEMICONDUCTOR DEVICE AND METHOD FOR MANUFACTURING SEMICONDUCTOR DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a highly reliable semiconductor device including a thin film transistor with stable electric characteristics, and to manufacture the highly reliable semiconductor device with high productivity and at a low cost.SOLUTION: A method for manufacturing a semiconductor device comprises a thin film transistor in which a semiconductor layer including a channel formation region, a source region, and a drain region are formed using an oxide semiconductor layer. In the method for manufacturing the semiconductor device, heat treatment (heat treatment for dehydration or dehydrogenation) for increasing purity of the oxide semiconductor layer and reducing moisture and the like as impurities is performed. Also, the heat-treated oxide semiconductor layers are slowly cooled under an oxygen atmosphere.