A thin-film transistor (TFT) includes a gate electrode, a semiconductor pattern, a source electrode, and a drain electrode. The semiconductor pattern includes an active layer being overlapped with the gate electrode and a low band gap portion having a lower energy band gap than the active layer. The source and drain electrodes are spaced apart from each other to be overlapped with the semiconductor pattern. Therefore, the semiconductor pattern includes a low band gap portion having a lower energy band gap than the active layer, so that electron mobility may be increased in a channel formed along the low band gap portion so that electric characteristics of the TFT may be enhanced.