A thin film transistor and a method of manufacturing the same, and a display device and a method of manufacturing the same are disclosed, in which the thin film transistor substrate comprises an active layer formed on a substrate; a gate electrode controlling electron transfer within the active layer; a source electrode connected with one end area of the active layer; a drain electrode connected with the other end area of the active layer; and a light-shielding layer formed under the active layer to shield light from entering the active layer.