To suppress a change in electrical characteristics and improve reliability in a transistor. The transistor includes a first gate electrode, a first insulating film over the first gate electrode, a second insulating film over the first insulating film, an oxide semiconductor film over the second insulating film, a source electrode electrically connected to the oxide semiconductor film, a drain electrode electrically connected to the oxide semiconductor film, a third insulating film over the oxide semiconductor film, a fourth insulating film over the third insulating film, a second gate electrode over the fourth insulating film, and a fifth insulating film over the second gate electrode. One or more of the second insulating film, the third insulating film, and the fourth insulating film include a halogen element. The halogen element is detected from one or more of a top surface, a bottom surface, and a side surface of the oxide semiconductor film.