The embodiments of the present disclosure relate to an array substrate, a thin film transistor, methods for fabricating the same, and a display device. The method for fabricating the array substrate provided by the embodiments of the present disclosure comprises: forming an active layer on a substrate; forming a gate on the active layer; forming a first insulation layer on the gate; forming a light blocking portion on the first insulation layer, the light blocking portion being arranged above an edge portion of the gate, so that the light blocking portion blocks light entering the active layer from the edge portion of the gate.