A thin-film transistor array substrate includes a substrate; a first active layer of a first transistor, which is on the substrate and includes a source region, a channel region, and a drain region; a conductive layer, which is on the first active layer and is electrically connected to the source region or the drain region via a contact hole; a first insulating layer and a second insulating layer, which are between the first active layer and the conductive layer, where the contact hole is defined through the first and second insulating layers; and a first supporting layer, which is between the first insulating layer and the second insulating layer and surrounds at least a portion of the contact hole.