| abstract |
A transistor including a self-aligned oxide semiconductor film, which has high electrical characteristics and has stable electrical characteristics. By performing heat treatment in an inert gas atmosphere in a state where the oxide semiconductor film and the metal film are in contact with each other, an element of the metal film is introduced into the oxide semiconductor film so that the resistance is higher than that of the channel formation region. Low resistance region is formed. Further, in the heat treatment, the metal film becomes a metal oxide insulating film in a region in contact with the oxide semiconductor film. Thereafter, unnecessary regions of the metal film are removed. Thus, a metal oxide insulating film can be formed on the low resistance region. Further, diffusion of impurities entering the oxide semiconductor film from the outside or oxygen released from the oxide semiconductor film can be suppressed by the metal oxide insulating film. [Selection] Figure 1 |