A method of fabricating an array substrate and a display device including the array substrate are discussed. According to an embodiment, the array substrate includes a gate electrode formed on a substrate; a gate insulating layer formed on the gate electrode; an oxide semiconductor layer and an etch prevention layer formed on the gate insulating layer, wherein ends of the oxide semiconductor layer and ends of the etch prevention layer are aligned with each other; source and drain electrodes formed on the etch prevention layer; a passivation layer including a contact hole formed on the source and drain electrodes and on the gate insulating layer; and a pixel electrode formed on the passivation layer and through the contact hole.