SEMICONDUCTOR DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a highly-reliable semiconductor device which uses an oxide semiconductor and is capable of suppressing variations in electric characteristics.SOLUTION: There is provided a semiconductor device which comprises: a first oxide semiconductor layer in contact with a source electrode layer and a drain electrode layer; and a second oxide semiconductor layer which serves as a current path (channel) of a transistor. The first oxide semiconductor layer functions as a buffer layer for preventing constituent elements of the source electrode layer and the drain electrode layer from spreading into a channel. Providing the first oxide semiconductor layer can prevent the constituent elements from spreading into an interface between the first oxide semiconductor layer and the second oxide semiconductor layer and into the second oxide semiconductor layer.