A display device comprising one or more thin-film transistors (“TFTs”) each configured to include an active layer, a gate insulating layer, a gate electrode, a source electrode, and a drain electrode are formed on a substrate. A storage capacitor including a first storage electrode and a second storage electrode overlapping the first storage electrode with the gate insulating layer interposed there between is also formed on the substrate. A top surface of the first storage electrode may include hillocks and the gate insulating layer is formed between the first storage electrode and the second storage electrode to conform to the shape of the top surface of the first storage electrode with the hillocks.