Semiconductor device and method for fabricating semiconductor device

A semiconductor device according to an embodiment includes a gate electrode, a first dielectric film, an oxide semiconductor film, a second dielectric film, a source electrode and a drain electrode. The first dielectric film is placed above the gate electrode. The oxide semiconductor film is placed above the first dielectric film. 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 the source electrode side and a film portion of the second contact region projects toward the drain electrode side.