Provided are a thin film transistor, a method for preparing the same and a flat panel display employing the same. The thin film transistor includes a gate electrode, source and drain electrodes insulated from the gate electrode, a semiconductor layer insulated from the gate electrode and electrically connected to the source and drain electrodes, an insulating layer, and a carrier blocking layer interposed between the semiconductor layer and the insulating layer and preventing electrons or holes moving through semiconductor layer from being trapped in the insulating layer. Since the thin film transistor is constructed such that the carrier blocking layer is interposed between the semiconductor layer and the insulating layer, the electrons or holes injected into the semiconductor layer can be prevented from being trapped in the insulating layer, thereby suppressing hysteresis characteristic. In addition, a reliable flat panel display device can be manufactured using the thin film transistor.