Patent ID: 7026683

Claim:
A nonvolatile semiconductor memory device comprising: a first conductive type semiconductor substrate including a plurality of trenches formed on a main surface of the semiconductor substrate; a plurality of nonvolatile memory elements formed on element regions respectively isolated by element isolation films formed in the trenches; the nonvolatile semiconductor memory elements comprising: a gate insulating film formed on the main surface of the semiconductor substrate; a plurality of floating electrodes formed along a first direction on the gate insulating film, the plurality of floating electrodes adjacent to each other along the first direction being electrically isolated by a plurality of grooves on the element isolation films; groove insulating films filled in said plurality of the grooves; a plurality of second conductive type impurity diffusion regions formed along a second direction so as to sandwich the floating electrodes; interelectrode insulating films formed along the first direction on the plurality of floating electrodes and the groove insulating films; and control electrodes formed on the interelectrode insulating films, wherein a width of one of the plurality of grooves is less than or equal to 1.6 times a film thickness of one of the interelectrode insulating films.