A thin film transistor including a substrate; a first gate electrode on the substrate; a first insulating layer covering the substrate and the first gate electrode; a semiconductor on the first insulating layer and overlapping the first gate electrode; a second insulating layer covering the first insulating layer and the semiconductor; a second gate electrode on the second insulating layer and crossing the first gate electrode in plane; a third insulating layer covering the second gate electrode and the second insulating layer; a first source electrode and a first drain electrode on the third insulating layer and connected to the semiconductor; and a second source electrode and a second drain electrode on a same layer as the first source electrode and the first drain electrode and connected to the semiconductor.