An organic light emitting diode (OLED) display device having a pixel area and a pad area. The pad area includes a silicon layer pattern arranged on the substrate, an insulating layer arranged on the silicon layer pattern, an interconnection layer arranged on the insulating layer, and a protective layer surrounding an edge of the interconnection layer and having an opening exposing the interconnection layer. Since a surface area of the interconnection layer is increased due to a roughness of the underlying polycrystalline silicon layer pattern in the pad area, resulting in increased contact area and reduced contact resistance between parts configured to operate a flat panel display device and the interconnection layer is increased.