Over the top of a semiconductor substrate, a lamination pattern having a control gate electrode, a first insulation film thereover, and a second insulation film thereover is formed. Over the top of the semiconductor substrate, a memory gate electrode adjacent to the lamination pattern is formed. Between the control gate electrode and the semiconductor substrate, a third insulation film for gate insulation film is formed. Between the memory gate electrode and the semiconductor substrate, and between the lamination pattern and the memory gate electrode, a fourth insulation film including a lamination film of a silicon oxide film, a silicon nitride film, and another silicon oxide film is formed. At the sidewall on the side of the lamination pattern adjacent to the memory gate electrode, the first insulation film is retreated from the control gate electrode and the second insulation film, and the upper end corner portion of the control gate electrode is rounded.