The present invention provides an array substrate, a method for manufacturing an array substrate, and a display device which are such that reflow failure of a resist mask does not occur readily at the time of manufacture of the array substrate, so the array substrate can be manufactured reliably. At the time of forming a TFT, third wiring 37 between source wiring 13 and the source electrode 22 of the TFT is provided with a narrow portion 38 that is formed with a narrow width by narrowing a midpoint at a portion of the wiring in planar shape, and the resist film on the source electrode 22 and a drain electrode 23 is reflowed so as to cover the surface of a channel region Q, thus forming a reflowed resist film 42. A semiconductor film 20 is etched using this as the etching mask in a state in which the area between the source and the drain is protected, thus making the semiconductor film 20 into an island shape.