| 摘要 |
PROBLEM TO BE SOLVED: To provide the structure of a semiconductor device using an oxide semiconductor for a semiconductor layer, which has excellent ON/OFF ratio property and high field effect mobility.SOLUTION: An oxide semiconductor layer comprises: a first oxide semiconductor film that bears a function as a carrier path as a main purpose; and a second oxide semiconductor film sandwiched between the first oxide semiconductor film and a gate insulating layer in a contact state for reducing an interface state as a main purpose. The first and second oxide semiconductor films are constituted of films containing the same metallic element as main components, and the electron affinity of the second oxide semiconductor film is set so as to be smaller than the electron affinity of the first oxide semiconductor film by 0.1 eV or more. Also, in the first oxide semiconductor film, a step portion is disposed at a position where the step portion is not overlapped with the second oxide semiconductor film, and overlapped with a source electrode, and at a position where the step portion is not overlapped with the second oxide semiconductor film, and overlapped with a drain electrode, and the source electrode and the drain electrode are brought into contact with the bottom face and side face of the step portion. |
