Semiconductor device and method for fabricating semiconductor device

A semiconductor device comprising:

• a gate electrode;
• a first dielectric film placed above the gate electrode;
• an oxide semiconductor film placed above the first dielectric film;
• a second dielectric film placed above the oxide semiconductor film;
• a source electrode placed in the second dielectric film and connected to the oxide semiconductor film;
• and
• a drain electrode placed in the second dielectric film and connected to the oxide semiconductor film,
• wherein the oxide semiconductor film is formed to have a film thickness in a first contact region in contact with the source electrode and a second contact region in contact with the drain electrode larger than a film thickness in a channel region of the oxide semiconductor film so that a film portion of the first contact region projects toward a source electrode side and a film portion of the second contact region projects toward a drain electrode side,
• wherein nitrogen concentration of an upper portion of the first contact region, in contact with the source electrode, of the oxide semiconductor film and nitrogen concentration of an upper portion of the second contact region, in contact with the drain electrode, of the oxide semiconductor film are higher than nitrogen concentration of the channel region of the oxide semiconductor film, the upper portions being at positions higher than a top surface of the channel region.