Abstract: Provided herein is a semiconductor device including a substrate; an active layer formed on top of the substrate; a protective layer formed on top of the active layer and having a first aperture; a source electrode, driving gate electrode and drain electrode formed on top of the protective layer; and a first additional gate electrode formed on top of the first aperture, wherein an electric field is applied to the active layer, protective layer and driving gate electrode due to a voltage applied to each of the source electrode, drain electrode and driving gate electrode, and the first additional gate electrode is configured to attenuate a size of the electric field applied to at least a portion of the active layer, protective layer and driving gate electrode.