Semiconductor device and method of manufacturing same

A semiconductor device, comprising:

• a semiconductor substrate having a first region and a second region arranged along a main surface thereof;
• a control gate electrode formed over the semiconductor substrate via a first insulating film;
• a second insulating film having therein a charge retention portion and a memory gate electrode formed successively over the main surface of the semiconductor substrate in a region adjacent to one of side walls of the control gate electrode;
• and
• a source region and a drain region formed in the main surface of the semiconductor substrate so as to sandwich therebetween the control gate electrode and the memory gate electrode,
• wherein the memory gate electrode is adjacent to the control gate electrode via the second insulating film,
• wherein the control gate electrode, the memory gate electrode, the source region, and the drain region configure memory cells of a nonvolatile memory,
• wherein the memory cells are formed in the first region and the second region, respectively, and
• wherein a bottom surface of the second insulating film in the first region is positioned below a bottom surface of the first insulating film and a bottom surface of the second insulating film in the second region.