A semiconductor device includes a transistor configuration including first and second gate electrodes, each of the first and second gate electrodes having at least a bottom layer and an upper layer including polycrystalline silicon grains, wherein the first gate electrode is a nMOS gate electrode formed in an nMOS region of the transistor configuration, wherein the polycrystalline silicon grains included in the bottom layer of the first gate electrode have a greater particle diameter than the polycrystalline grains included in the upper layer of the second gate electrode.