SEMICONDUCTOR DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a display device which operates stably by using a transistor having stable electrical characteristics.SOLUTION: In manufacturing a display device by applying a transistor with an oxide semiconductor layer as a channel formation region, an additional gate electrode is disposed on at least a transistor applied to a drive circuit. In manufacturing a transistor with an oxide semiconductor layer as a channel formation region, heat treatment for dehydration or dehydrogenation is performed to the oxide semiconductor layer to reduce an impurity such as moisture and the like existing in the interfaces of the oxide semiconductor layer with a gate insulating layer and a protective insulation layer which are disposed above and below in contact therewith.