Semiconductor device and display device including the semiconductor device

A semiconductor device comprising:

• a transistor comprising:
• a conductive film;
• a first insulating film over the conductive film;
• an oxide semiconductor film over the first insulating film;
• a second insulating film over the oxide semiconductor film;
• a gate electrode over the second insulating film;
• a metal oxide film in contact with a side surface of the second insulating film and a side surface of the gate electrode;
• and
• a third insulating film over the oxide semiconductor film, the gate electrode, and the metal oxide film,
• wherein the oxide semiconductor film comprises a channel region overlapping with the gate electrode, a source region in contact with the third insulating film, and a drain region in contact with the third insulating film,
• wherein each of the source region and the drain region comprises any one or more of hydrogen, boron, carbon, nitrogen, fluorine, phosphorus, sulfur, chlorine, titanium and a rare gas, and
• wherein the first insulating film is in contact with the metal oxide film in a channel width direction of the transistor.

A semiconductor device comprising:

• a transistor comprising:
• an oxide semiconductor film over a first insulating film;
• a second insulating film over the oxide semiconductor film;
• a gate electrode over the second insulating film;
• a metal oxide film in contact with a side surface of the second insulating film and a side surface of the gate electrode;
• and
• a third insulating film over the oxide semiconductor film, the gate electrode, and the metal oxide film,
• wherein the oxide semiconductor film comprises a channel region overlapping with the gate electrode, a source region in contact with the third insulating film, and a drain region in contact with the third insulating film, and
• wherein the first insulating film is in contact with the metal oxide film in a channel width direction of the transistor.