A semiconductor device includes a dual-gate transistor including an oxide semiconductor film between a first gate electrode and a second gate electrode, a gate insulating film between the oxide semiconductor film and the second gate electrode, and a pair of electrodes in contact with the oxide semiconductor film. The semiconductor device further includes an insulating film over the gate insulating film, and a conductive film over the insulating film and connected to one of the pair of electrodes. The insulating film includes an opening in at least a region overlapping with the oxide semiconductor film in which the second gate electrode is provided in contact with the gate insulating film. The second gate electrode is formed using the same material as the conductive film connected to the one of the pair of electrodes.