Semiconductor device including oxide semiconductor film

摘要

A highly reliable semiconductor device having stable electrical characteristics is provided. Oxide films each containing one or more kinds of metal elements included in an oxide semiconductor film are formed in contact with an upper side and a lower side of the oxide semiconductor film where a channel is formed, whereby interface states are not easily generated at an upper interface and a lower interface of the oxide semiconductor film. A material which has a lower electron affinity than the oxide semiconductor film is used for the oxide films in contact with the oxide semiconductor film, whereby electrons flowing in the channel hardly move in the oxide films and mainly move in the oxide semiconductor film. Thus, even when an interface state exists between the oxide film and an insulating film formed on the outside of the oxide film, the state hardly influences the movement of electrons.

主权项

1. A semiconductor device comprising:
a first electrode; a first insulating film over the first electrode; an oxide semiconductor film comprising gallium over the first insulating film; a first oxide film over and in contact with the oxide semiconductor film; a second electrode over the first oxide film; a third electrode over the first oxide film; and a second oxide film over and in contact with the first oxide film, the second electrode, and the third electrode, and wherein each of the first oxide film and the second oxide film comprises indium, gallium, and zinc, wherein electron affinity of the second oxide film is equal to or lower than electron affinity of the first oxide film, and wherein the electron affinity of the second oxide film is lower than electron affinity of the oxide semiconductor film.