Semiconductor device and a method of manufacturing the same

A semiconductor device, comprising:

• a first MISFET including a first gate formed over a principal surface of a semiconductor substrate through a first insulating film;
• a second MISFET including a second gate which is thicker than the first gate, formed over the principal surface of the semiconductor substrate through a second insulating film which is thicker than the first gate insulating film;
• and
• a memory cell including a control gate formed over the principal surface of the semiconductor substrate through a third gate insulating film, a charge storage layer in which one part thereof is formed at one sidewall of the control gate as well as the other part thereof is formed over the principal surface of the semiconductor substrate, and a memory gate which is electrically separated from the control gate through the one part of the charge storage layer, as well as electrically separated from the semiconductor substrate through the other part of the charge storage layer, forming a split gate together with the gate control gate, and
• wherein the third gate insulating film is thinner than the second gate insulating film, the control gate is thicker than the first gate and the ratio of height of the memory gate with respect to the gate length of the memory gate is larger than 1.