Provided are a display device, a method of fabricating the display device, and a method of fabricating an image sensor device. The method of fabricating the display device includes preparing a substrate including a cell array area and a peripheral circuit area, forming a silicon layer on the peripheral circuit area of the substrate, forming oxide layers on the cell array area and the peripheral circuit area of the substrate, forming gate dielectric layers on the silicon layer and the oxide layers, forming the gate electrodes on the gate dielectric layers, wherein the gate electrodes expose both ends of the silicon layer and both ends of the oxide layers, and injecting dopant into both ends of the silicon layer and both ends of the oxide layers at the same time.