Nonvolatile semiconductor storage device and manufacturing method therefor

A nonvolatile semiconductor storage device comprising:

• a semiconductor substrate;
• a plurality of isolation regions formed in the semiconductor substrate;
• an element-forming region formed between adjacent isolation regions;
• a first gate insulating film provided on the element-forming region;
• a floating gate electrode provided on the first gate insulating film;
• a second gate insulating film provided on the floating gate electrode;
• and
• a control gate electrode provided on the second gate insulating film,
• wherein a width of at least a part of a body of the element-forming region is narrower than a width of a top surface of the element-forming region in a section taken in a direction perpendicular to a direction in which the isolation regions extend.

A manufacturing method of a nonvolatile semiconductor storage device comprising:

• forming a first gate insulating film on a semiconductor substrate;
• depositing a material for floating gate electrodes on the first gate insulating film;
• forming a plurality of trenches which extend through the material for the floating gate electrodes and the first gate insulating film and reach the semiconductor substrate;
• etching side walls of the material for the floating gate electrodes to form the floating gate electrodes such that a lower hem of the material for the floating gate electrodes facing an element-forming region is narrower than a width of a surface of the element-forming region in a section taken in a direction perpendicular to a direction in which the trenches extend;
• forming second gate insulating films on the floating gate electrodes;
• and
• forming control gate electrodes on the second gate insulating films.

A manufacturing method of a nonvolatile semiconductor storage device comprising:

• forming a first gate insulating film on a semiconductor substrate;
• depositing a material for floating gate electrodes on the first gate insulating film;
• forming a plurality of trenches which extend through the material for the floating gate electrodes and the first gate insulating film and which reach the semiconductor substrate, and forming an element-forming region in which a width of at least a part of a body is narrower than a width of a top surface in a section taken in a direction perpendicular to a direction in which the trenches extend;
• forming a second gate insulating film on the material for the floating gate electrodes;
• and
• forming a control gate electrode on the second gate insulating film.