A substrate including a thin film transistor, the substrate including an active layer disposed on the substrate, the active layer including a channel area and source and drain areas, a gate electrode disposed on the active layer, the channel area corresponding to the gate electrode, a gate insulating layer interposed between the active layer and the gate electrode, an interlayer insulating layer disposed to cover the active layer and the gate electrode, the interlayer insulating layer having first and second contact holes partially exposing the active layer, source and drain electrodes disposed on the interlayer insulating layer, the source and drain areas corresponding to the source and drain electrodes, and ohmic contact layers, the ohmic contact layers being interposed between the interlayer insulating layer and the source and drain electrodes, and contacting the source and drain areas through the first and second contact holes.