Semiconductor device
The oxide semiconductor film has the top and bottom surface portions each provided with a metal oxide film containing a constituent similar to that of the oxide semiconductor film. An insulating film containing a different constituent from the metal oxide film and the oxide semiconductor film is further formed in contact with a surface of the metal oxide film, which is opposite to the surface in contact with the oxide semiconductor film. The oxide semiconductor film used for the active layer of the transistor is an oxide semiconductor film highly purified to be electrically i-type (intrinsic) by removing impurities such as hydrogen, moisture, a hydroxyl group, and hydride from the oxide semiconductor and supplying oxygen which is a major constituent of the oxide semiconductor and is simultaneously reduced in a step of removing impurities.
1. A semiconductor device comprising:
a pixel portion including a first transistor; and
a driver circuit comprising a second transistor,
wherein each of the first transistor and the second transistor comprises:
a first gate electrode over a substrate;
a first metal oxide film over the first gate electrode;
an oxide semiconductor film in contact with the first metal oxide film;
a source electrode and a drain electrode in contact with the oxide semiconductor film; and
a second metal oxide film in contact with the oxide semiconductor film,
wherein each of the first metal oxide film and the second metal oxide film comprises one or more constituent metal elements of the oxide semiconductor film, and
wherein the second transistor further comprises a second gate electrode over the second metal oxide film.
2. The semiconductor device according to claim 1 , wherein at least part of a top surface of the oxide semiconductor film is in contact with the source electrode and the drain electrode.
3. The semiconductor device according to claim 1 , wherein the first metal oxide film and the second metal oxide film each have a larger energy gap than the oxide semiconductor film.
4. The semiconductor device according to claim 1 , wherein an energy at a bottom of a conduction band of each of the first metal oxide film and the second metal oxide film is higher than an energy at a bottom of a conduction band of the oxide semiconductor film.
5. The semiconductor device according to claim 1 , wherein the oxide semiconductor film comprises In, Ga, and Zn.
6. A semiconductor device comprising:
a pixel portion including a first transistor and a light-emitting element; and
a driver circuit comprising a second transistor,
wherein each of the first transistor and the second transistor comprises:
a first gate electrode over a substrate;
a first oxide film over the substrate;
an oxide semiconductor film over the first oxide film, wherein the oxide semiconductor film and the first gate electrode overlap with each other;
a source electrode and a drain electrode over the first oxide film; and
second oxide film over the oxide semiconductor film, the second oxide film having an island-shaped,
wherein a bottom surface of the oxide semiconductor film of the first transistor is in contact with a top surface and a side surface of each of the source electrode and the drain electrode of the first transistor,
wherein a bottom surface of the oxide semiconductor film of the second transistor is in contact with a top surface and a side surface of each of the source electrode and the drain electrode of the second transistor,
wherein the second transistor further comprises a second gate electrode overlapping with the second oxide film and the first gate electrode of the second transistor,
wherein the second gate electrode of the second transistor has the same potential as the first gate electrode of the second transistor, and
wherein one of the source electrode and the drain electrode of the first transistor is electrically connected to a pixel electrode of the light-emitting element.
7. The semiconductor device according to claim 6 , wherein each of the first oxide film and the second oxide film is a metal oxide film.
8. The semiconductor device according to claim 6 , wherein the oxide semiconductor film comprises In, Ga, and Zn.
9. The semiconductor device according to claim 6 , wherein the first gate electrode comprises a layered structure including a titanium layer and an aluminum layer.
10. The semiconductor device according to claim 6 , wherein each of the source electrode and the drain electrode comprises a molybdenum film.