A display device is provided. The display device comprises a substrate, a first buffer layer on the substrate, a first semiconductor layer on the first buffer layer and including a first active layer, a first gate insulating layer on the first semiconductor layer and the first buffer layer and covering the first active layer, a first conductive layer on the first gate insulating layer and including a first gate electrode, a second conductive layer on the first conductive layer and including a first source/drain electrode, a first interlayer insulating layer on the first conductive layer, a second semiconductor layer on the first interlayer insulating layer and including a second active layer, a second gate insulating layer on the second semiconductor layer and covering the second active layer, and a third conductive layer on the second gate insulating layer and including a second gate electrode and a second source/drain electrode, wherein the first gate insulating layer and the second gate insulating layer include different insulating materials.