A thin film transistor, e.g., for use in an organic light emitting display, may include: a gate insulating layer disposed on a gate electrode located on a substrate; a semiconductor layer, disposed on the gate insulating layer; and a planarization layer disposed on the gate insulating layer, the source and drain electrodes, and the channel area, and having openings exposing parts of the first source and drain areas and the source and drain electrodes, respectively. The semiconductor layer may include: a channel area corresponding to the gate electrode; first source and drain areas doped with an impurity outside the channel area; second source and drain areas, including a metal, outside the first source and drain areas; and source and drain electrodes disposed on the second source and drain areas and exposing the first source and drain areas. A pixel electrode may be disposed in one of the openings.