A display device has a thin film transistor on a substrate. The thin film transistor includes a first transistor having an oxide semiconductor film, a first gate insulating film, and a first gate electrode and a second transistor having a silicon semiconductor film, a second gate insulating film, and a second gate electrode. The first gate insulating film includes a first insulating film and a second insulating film. The oxide semiconductor film is positioned between the first insulating film and the substrate. The first insulating film is positioned between the silicon semiconductor film and the substrate and between the second insulating film and the substrate. The second gate insulating film includes an insulating film made of the same material in the same layer as the second insulating film. The first gate electrode and the second gate electrode are in the same layer.