Nonvolatile semiconductor memory device

an electrically erasable and programmable nonvolatile semiconductor memory device, comprising:

• a first conductivity-type semiconductor substrate;
• a second conductivity-type source region and a drain region disposed apart to face each other on a surface of the semiconductor substrate;
• a channel formation region sandwiched by the source region and the drain region, formed on the surface of the semiconductor substrate;
• a floating gate electrode disposed on a gate insulating film over the source region, the drain region and the channel region;
• a control gate electrode disposed on a control insulating film over the floating gate electrode and capacitively coupled to the floating gate electrode;
• a tunnel region disposed in a part of the drain region;
• and
• a tunnel insulating film disposed between a surface of the tunnel region and the floating gate electrode;
• wherein the tunnel region and a peripheral region around the tunnel region is made lower, and a depletion electrode, to which a predetermined potential is given to deplete a part of the tunnel region through a depletion electrode insulating film, is arranged in a lowered drain.