A thin-film transistor (TFT) array substrate includes a TFT arrangement and a storage capacitor. A gate insulation layer has a portion interposed between two electrode plates of the storage capacitor and thinner than a remaining portion of the gate insulation layer and thus, the thickness of insulation between the electrode plates of the storage capacitor is reduced so that the area of the opposite surfaces of the capacitor can be made smaller and an increased aperture ratio can be achieved.