A display device includes a base substrate; an oxide semiconductor layer disposed on the base substrate; a first gate insulating layer disposed on a first channel region of the oxide semiconductor layer and that overlaps the first channel region thereof; a first upper gate electrode disposed on the first gate insulating layer; and an upper interlayer insulating layer disposed on the first upper gate electrode, the first upper gate electrode, and the oxide semiconductor layer, wherein the upper interlayer insulating layer includes a first upper interlayer insulating layer, a second upper interlayer insulating layer, and a third upper interlayer insulating layer, the first upper interlayer insulating layer includes silicon oxide, each of the second and third upper interlayer insulating layers include silicon nitride, and a hydrogen concentration in the second upper interlayer insulating layer is less than a hydrogen concentration in the third upper interlayer insulating layer.