An organic light emitting diode display device comprises a driving thin film transistor including a first semiconductor layer, a gate insulating layer formed on the first semiconductor layer. The device further includes a storage capacitor including a first capacitor electrode electrically coupled to a drain electrode of the driving thin film transistor, a buffer layer formed on the first capacitor electrode, a second semiconductor layer formed on the buffer layer, and a second capacitor electrode formed on the second semiconductor layer and electrically coupled to a gate electrode of the driving thin film transistor. The device also includes an organic light emitting diode connected to the drain electrode of the driving transistor. The gate insulating layer has at least one hole in a region where the gate insulating layer overlaps the second semiconductor layer, thereby exposing the second semiconductor layer to the second capacitor electrode.