Semiconductor device and method for manufacturing the same

A semiconductor device comprising:

• a first oxide semiconductor film comprising a channel formation region;
• a second oxide semiconductor film comprising In, Al, and Zn;
• and
• an electrode electrically connected to the first oxide semiconductor film through the second oxide semiconductor film,
• wherein the second oxide semiconductor film comprises a first region in contact with the electrode and not overlapping with the first oxide semiconductor film,
• wherein the second oxide semiconductor film comprises a second region in contact with the first oxide semiconductor film, and
• wherein a resistance of the first region is lower than a resistance of the second region.

A semiconductor device comprising:

• a gate electrode;
• an insulating layer over the gate electrode;
• a first oxide semiconductor film over the insulating layer, the first oxide semiconductor film comprising a channel formation region;
• a second oxide semiconductor film over the first oxide semiconductor film, the second oxide semiconductor film comprising In, Al, and Zn;
• and
• an electrode over the second oxide semiconductor film,
• wherein the second oxide semiconductor film comprises a first region in contact with the electrode and not overlapping with the first oxide semiconductor film,
• wherein the second oxide semiconductor film comprises a second region in contact with the first oxide semiconductor film, and
• wherein a resistance of the first region is lower than a resistance of the second region.

A semiconductor device comprising:

• a gate electrode;
• an insulating layer over the gate electrode;
• a first oxide semiconductor film over the insulating layer, the first oxide semiconductor film comprising a channel formation region;
• a second oxide semiconductor film over and in direct contact with the first oxide semiconductor film, the second oxide semiconductor film comprising In, Al, and Zn;
• and
• an electrode over the second oxide semiconductor film,
• wherein the second oxide semiconductor film comprises a first region in direct contact with the electrode and not overlapping with the first oxide semiconductor film,
• wherein the second oxide semiconductor film comprises a second region in contact with the first oxide semiconductor film, and
• wherein a resistance of the first region is lower than a resistance of the second region.