Provided are a Thin Film Transistor (TFT) and a method of manufacturing the same. The TFT includes a gate electrode; a source electrode and a drain electrode spaced from the gate electrode in a vertical direction and spaced from each other in a horizontal direction; a gate insulation layer disposed between the gate electrode and the source and drain electrodes; and an active layer disposed between the gate insulation layer and the source and drain electrodes. The active layer is formed of a conductive oxide layer and comprises at least two layers having different conductivities according to an impurity doped into the conductive oxide layer.