A flat panel display device having a high capacitance and a high aperture ratio. A thin film transistor and a capacitor are formed on an insulating substrate. The thin film transistor includes a semiconductor layer, a gate electrode and source and drain electrodes. The capacitor has first and second capacitor electrodes and a dielectric layer. An insulating layer is formed over the transistor to insulate the gate electrode from the source and drain electrodes, and a portion of the insulating layer is formed as the dielectric layer between the first and second capacitor electrodes. A non-planar shape of the first capacitor electrode and a conforming shape of the dielectric layer and a second capacitor electrode increase a capacitance of the capacitor. The portion of the insulating layer serving as the capacitor dielectric is formed to be thinner than the portion of the insulating layer formed over the gate electrode.