A thin-film transistor, method of manufacturing the same, and organic light-emitting diode (OLED) display including the same are disclosed. In one aspect, the thin-film transistor includes an active layer including a channel region, a source region, and a drain region, wherein the active layer has a top surface. The transistor also includes a gate insulating layer formed over the active layer and a gate metal layer formed over the gate insulating layer and having a bottom surface. The area of the bottom surface of the gate metal layer is less than the area of the top surface of the active layer and the bottom surface of the gate metal layer overlaps the top surface of the active layer.