Semiconductor device and method for manufacturing semiconductor device

摘要

A highly reliable semiconductor device is manufactured by giving stable electric characteristics to a transistor in which an oxide semiconductor film is used for a channel. An oxide semiconductor film which can have a first crystal structure by heat treatment and an oxide semiconductor film which can have a second crystal structure by heat treatment are formed so as to be stacked, and then heat treatment is performed; accordingly, crystal growth occurs with the use of an oxide semiconductor film having the second crystal structure as a seed, so that an oxide semiconductor film having the first crystal structure is formed. An oxide semiconductor film formed in this manner is used for an active layer of the transistor.

主权项

1. A semiconductor device comprising:
a first insulating film; a second insulating film overlapping the first insulating film; a stack of semiconductor films interposed between the first insulating film and the second insulating film, the stack of semiconductor films comprising:
a first oxide semiconductor film; anda second oxide semiconductor film on and in contact with the first oxide semiconductor film; and a gate electrode, wherein the gate electrode and the stack of semiconductor films overlap, and wherein a concentration in nitrogen of the first oxide semiconductor film is higher than a concentration in nitrogen of the second oxide semiconductor film.