In a semiconductor device, a memory cell is formed of a control gate electrode and a memory gate electrode adjacent to each other, a gate insulating film formed below the control gate electrode and an insulating film formed below the memory gate electrode and having a charge accumulating part therein. Also, in this semiconductor device, a capacitive element is formed of a lower electrode, an upper electrode and a capacitive insulating film formed between the upper electrode and the lower electrode. A thickness of the lower electrode is smaller than a thickness of the control gate electrode.