The present provides a thin film transistor, which comprises: a gate on the substrate; a gate insulating layer; the embossed portion defining a first end in which a first active layer is formed, and a second end in which a second active layer is formed; a first source connected to the first active layer and a second source connected to the second active layer; a passivation layer; a first through hole and a second through hole defined in the passivation layer; and a drain formed on the passivation layer and extending through the first and second through hole to interconnect the first and second active layers, respectively. By this arrangement, a first distance defined between the drain with respect to a first contact surface of the first source layer located on the flattened portion of the embossed portion will equal to the height of the embossed portion. In addition, a second distance defined between the drain with respect to a second contact surface of the second source layer located on the flattened portion of the embossed portion will equal to the height of the embossed portion as well. By implementation of the technology provided by the present invention, a thin film transistor of shortened channel can be realized such that the thin film transistor is benefited with a larger aspect ratio so as to entertain a larger on-state current.