A thin film transistor (TFT), method of manufacturing the TFT and a flat panel display having the TFT are disclosed. In one aspect, the TFT comprises a substrate and an active layer formed over the substrate, wherein the active layer is formed of oxide semiconductor, and wherein the active layer includes two opposing sides. The TFT also comprises source and drain regions formed at the opposing sides of the active layer, a first insulating layer formed over the active layer, a gate electrode formed over the active layer, a second insulating layer formed covering the first insulation layer and the gate electrode, and a first conductive layer formed on the source and drain regions and contacting the second insulating layer.