Patent ID: 6906378

Claim:
A non-volatile semiconductor memory device comprising: a semiconductor substrate having a main surface provided with two spaced trenches; an isolation insulator filling said trench, said isolation insulator comprising a first oxide film and a second HDP-CVD oxide film, said second HDP-CVD oxide film having an upper surface extending downwardly toward said semiconductor substrate; a floating electrode having a flat surface and extending from the main surface of said semiconductor substrate between said two trenches to said two isolation insulators, wherein said upper surface of said second HDP-CVD oxide film is in contact with a portion of said floating electrode, and wherein said portion of said floating electrode, which is in contact with said upper surface of said second HDP-CVD oxide film, extends below said main surface of said semiconductor substrate; an insulation film extending from the upper surface of said floating electrode to a side surface of said floating electrode overlying said isolation insulator; and a control gate disposed on said insulation film to extend from the upper surface of said floating electrode to the side surface of said floating electrode.