An array substrate for a display device includes an insulating substrate, a buffer layer which is disposed on the insulating substrate and is formed of silicon oxide with a refractive index equal to a refractive index of the insulating substrate, a first insulation layer which is disposed on the buffer layer and formed of silicon nitride, a second insulation layer which is disposed on the first insulation layer and formed of silicon oxide, a switching element including a semiconductor layer disposed on the second insulation layer, and a pixel electrode connected to the switching element.