Method of manufacturing semiconductor device

A method of manufacturing a semiconductor device having a first region where a first MISFET being a part of a non-volatile memory cell is formed and a second region where a second MISFET is formed, the method comprising the steps of:

• (a) forming a first well of a first conductivity type in a semiconductor substrate;
• (b) forming a first resist pattern having an opening on the semiconductor substrate in the first region and covering the semiconductor substrate in the second region;
• (c) forming a first channel region of the first MISFET in a surface of the first well in the first region by ion implantation of an impurity of a second conductivity type that is opposite to the first conductivity type;
• (d) forming a nitrogen-introduction portion inside the first channel region by ion implantation of nitrogen using the first resist pattern as a mask;
• (e) after the step (d), removing the first resist pattern;
• (f) after the step (e), forming a first gate insulating film of the first MISFET having a trap insulating film that can retain electric charges, on the first channel region in the first region;
• and
• (g) after the step (f), forming a first gate electrode of the first MISFET on the first gate insulating film.