A flat panel display is provided. The flat panel display includes a light emitting device and two or more thin film transistors (TFTs) having semiconductor active layers having channel regions, where the thickness of the channel regions of the TFTs are different from each other. Thus, higher switching properties of a switching TFT can be maintained, a more uniform brightness of a driving TFT can be satisfied, and a white balance can be satisfied without changing a size of the TFT active layer.