A display device includes a substrate, a buffer layer on the substrate, a first semiconductor layer of a first transistor on the buffer layer, a first insulating layer disposed on the first semiconductor layer, a first gate electrode of the first transistor on the first insulating layer, a second insulating layer on the first gate electrode, and a second semiconductor layer of a second transistor disposed on the second insulating layer. A difference between a first distance between a lower side of the buffer layer and an upper side of the second insulating layer and a second distance between an upper side of the first semiconductor layer and an upper side of the second insulating layer is 420 to 520 angstroms.