To suppress a change in electrical characteristics in a transistor including an oxide semiconductor film. The transistor includes a first gate electrode, a first insulating film, an oxide semiconductor film, a source electrode, a drain electrode, a second insulating film, a second gate electrode, and a third insulating film. The oxide semiconductor film includes a first oxide semiconductor film on the first gate electrode side, and a second oxide semiconductor film over the first oxide semiconductor film. The first oxide semiconductor film and the second oxide semiconductor film include In, M, and Zn (M is Al, Ga, Y, or Sn). In a region of the second oxide semiconductor film, the number of atoms of In is smaller than that in the first oxide semiconductor film. The second gate electrode includes at least one metal element included in the oxide semiconductor film.