Semiconductor device and manufacturing method of semiconductor device

A semiconductor device, comprising:

• a semiconductor substrate;
• a first gate electrode disposed over the semiconductor substrate;
• a second gate electrode disposed over the semiconductor substrate so as to be adjacent to the first gate electrode;
• a first insulating film formed between the first gate electrode and the semiconductor substrate;
• a second insulating film formed between the second gate electrode and the semiconductor substrate, and between the first gate electrode and the second gate electrode, the second insulating film including a charge storing portion;
• a drain region disposed in the semiconductor substrate on the first gate electrode side, the drain region including a high concentration impurity diffusion layer and a first low concentration impurity diffusion layer;
• and
• a source region disposed in the semiconductor substrate on the second gate electrode side, the source region including a second low concentration impurity diffusion layer,
• wherein the source region has no impurity diffusion layer with an impurity concentration higher than that of the second low concentration impurity diffusion layer.