A method of manufacturing a flat panel display device includes: forming a semiconductor layer of a thin film transistor (TFT) on a substrate; forming a gate electrode on the semiconductor layer with a gate insulating layer between the gate electrode and the semiconductor layer, and doping source and drain regions of the semiconductor layer with ion impurities; sequentially forming a first conductive layer, a first insulating layer, and a second conductive layer, and forming a capacitor at a distance away from the TFT by patterning the first conductive layer, the first insulating layer, and the second conductive layer; forming a second insulating layer, and forming contact holes passing through the second insulating layer, the contact holes exposing portions of the source and drain regions and the second conductive layer; and forming source and drain electrodes that respectively contact the source and drain regions and the second conductive layer through the contact holes.