The performances of a semiconductor device are improved. A semiconductor device has a first electrode and a dummy electrode formed apart from each other over a semiconductor substrate, a second electrode formed between the first electrode and the dummy electrode, at the circumferential side surface of the first electrode, and at the circumferential side surface of the dummy electrode, and a capacitive insulation film formed between the first electrode and the second electrode. The first electrode, the second electrode, and the capacitive insulation film form a capacitive element. Further, the semiconductor device has a first plug penetrating through the interlayer insulation film, and electrically coupled with the first electrode, and a second plug penetrating through the interlayer insulation film, and electrically coupled with the portion of the second electrode formed at the side surface of the dummy electrode opposite to the first electrode side.