Nonvolatile semiconductor memory device having grooves isolating the floating electrodes of memory cells and method of manufacturing the nonvolatile semiconductor memory device

A method of manufacturing a nonvolatile semiconductor memory device, comprising:

• forming at least first and second element forming regions isolated by element isolation regions on a main surface of a first conductive type semiconductor substrate;
• forming first and second gate insulating films within the first and second element forming regions, respectively;
• forming first and second floating electrodes respectively on the first and second gate insulating films in a state of being isolated by grooves on the element isolation regions;
• forming a groove insulating film having the substantially same thickness as the first and second floating electrodes, in the groove;
• forming an interelectrode insulating film on the groove insulating film and on the first and second floating electrodes;
• and
• forming control electrodes so as to extend over the first and second floating electrodes on the interelectrode insulating film.

A method of manufacturing a nonvolatile semiconductor memory device, comprising:

• depositing a gate insulating layer on a main surface of a semiconductor substrate;
• depositing a first floating electrode layer on the gate insulating layer;
• patterning the first floating electrode layer and the gate insulating layer, thereby forming a gate insulating film and a first floating electrode;
• making an element isolation groove in the semiconductor substrate;
• filling the element isolation groove with an element isolation film, forming an element isolation region;
• forming a second floating electrode layer on the first floating electrode and element isolation film;
• patterning the second floating electrode layer, making an insulating groove in the second floating electrode and thus forming two second floating electrodes on the first floating electrode, which are isolated form each other;
• forming a groove insulating film which fills up the insulating groove;
• depositing an interelectrode insulating layer on the groove insulating film and the second floating electrodes;
• depositing a control electrode layer on the interelectrode insulating layer;
• and
• patterning the control electrode layer, thereby forming control electrodes, each on the groove insulating film and the second floating electrode.