Semiconductor device

摘要

High field-effect mobility is provided for a transistor including an oxide semiconductor. Further, a highly reliable semiconductor device including the transistor is provided. In a bottom-gate transistor including an oxide semiconductor layer, an oxide semiconductor layer functioning as a current path (channel) of the transistor is sandwiched between oxide semiconductor layers having lower carrier densities than the oxide semiconductor layer. In such a structure, the channel is formed away from the interface of the oxide semiconductor stacked layer with an insulating layer in contact with the oxide semiconductor stacked layer, i.e., a buried channel is formed.

主权项

1. A semiconductor device comprising:
a first oxide semiconductor film; a second oxide semiconductor film on and in contact with the first oxide semiconductor film; a third oxide semiconductor film on and in contact with the second oxide semiconductor film; a first oxide insulating film and a second oxide insulating film between which the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film are positioned; a gate electrode overlapping with the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film with the first oxide insulating film interposed therebetween; a source electrode and a drain electrode each electrically connected to at least one of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film, wherein the second oxide semiconductor film has a difference between a Fermi level and a bottom of a conduction band smaller than the first oxide semiconductor film and the third oxide semiconductor film.