Semiconductor device and a manufacturing method thereof

A method of manufacturing a semiconductor device comprising:

• (a) providing an SOI substrate including a semiconductor substrate, a first insulating film formed on the semiconductor substrate and a semiconductor layer formed on the first insulating film, the SOI substrate having a core region and a memory cell region;
• (b) removing the semiconductor layer and the first insulating film positioned in the memory cell region;
• (c) forming a second insulating film on the semiconductor layer in the core region, and forming a third insulating film including a charge accumulation part on the semiconductor substrate in the memory cell region;
• (d) forming a first gate electrode on the third insulating film and a second gate electrode on the second insulating film;
• (e) forming a fourth insulating film so as to cover the first gate electrode and the second gate electrode;
• (f) removing portions of the fourth insulating film by etching in the memory cell region, thereby forming first offset spacers formed of the fourth insulating film on side surfaces of the first gate electrode;
• (g) removing portions of the fourth insulating film by etching in the core region, thereby forming second offset spacers formed of the fourth insulating film on side surfaces of the second gate electrode;
• (h) forming a first gate insulating film formed of the third insulating film between the first gate electrode and the semiconductor substrate, by performing etching to portions of the third insulating film in a state that the first offset spacers are formed;
• and
• (i) forming a second gate insulating film formed of the second insulating film between the second gate electrode and the semiconductor layer, by performing etching to portions of the second insulating film in a state that the second offset spacers are formed.