A thin film transistor may include a substrate, a buffer layer on the substrate, a semiconductor layer formed on the buffer layer, a gate insulating pattern on the semiconductor layer, a gate electrode on the gate insulating pattern, an interlayer insulating layer covering the gate electrode and the gate insulating pattern, the interlayer insulating layer having a contact hole and an opening extending therethrough, the contact hole exposing a source area and a drain area of the semiconductor layer, and the opening exposing a channel area of the semiconductor layer, and a source electrode and a drain electrode formed on the interlayer insulating layer, the source electrode being connected with the source area and the drain electrode being connected with the drain area of the semiconductor layer.