A thin film transistor substrate, a method for fabricating the same, and a display device including the same are provided. In one aspect of the present invention, there is provided a thin film transistor substrate comprising a substrate, a semiconductor layer formed on the substrate, a gate insulating film formed on the semiconductor layer, a gate electrode formed on the gate insulating film, an interlayer insulating film formed on the gate electrode and including a source contact hole and a drain contact hole for exposing portions of the semiconductor layer, and a source electrode and a drain electrode respectively inserted into the source contact hole and the drain contact hole. The interlayer insulating film includes a first convex portion formed at an inlet of the source contact hole and at an inlet of the drain contact hole.