A display device is provided, which includes a substrate including a pixel region; a metal oxide semiconductor transistor disposed over the substrate and including: a metal oxide semiconductor layer, a first gate electrode overlapping with the metal oxide semiconductor layer; and a gate insulating layer disposed between the metal oxide semiconductor layer and the first gate electrode, and the gate insulating layer having a first opening, wherein the first opening and the pixel region overlap; a second insulating layer disposed over the metal oxide semiconductor layer and having a via and a second opening, wherein the second opening and the pixel region overlap; and a pixel electrode electrically connected to the metal oxide semiconductor layer through the via.