The present invention relates to a thin film transistor, a method thereof and an organic light emitting device including the thin film transistor. According to an embodiment of the present invention, the thin film transistor includes a substrate, a control electrode, an insulating layer, a first electrode and a second electrode, a first ohmic contact layer and a second ohmic contact layer, and a semiconductor layer. The control electrode is formed on the substrate, and the insulating layer is formed on the control electrode. The first and the second electrodes are formed on the insulating layer. The first ohmic contact layer and the second ohmic contact layer are formed on the first electrode and the second electrode. The semiconductor layer is formed on the first ohmic contact layer and the second ohmic contact layer to fill between the first and the second electrodes.