Nonvolatile semiconductor memory device and method of manufacturing the same
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorShu Shimizu
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Abstract
A nonvolatile semiconductor memory device includes a semiconductor substrate having a main surface, a floating gate electrode having a doped polycrystalline silicon film formed on the main surface with a thermal oxide film therebetween, and a doped polycrystalline silicon film laid over the doped polycrystalline silicon film and having an upward wall, an insulating film covering the doped polycrystalline silicon film, and a control gate electrode formed on the insulating film.
Claims13
A nonvolatile semiconductor memory device comprising:
- a semiconductor substrate having a main surface;
- a floating gate electrode having a first conductive film formed on said main surface with a tunnel insulating film therebetween, and a second conductive film laid over said first conductive film and having a convexity;
- an insulating film covering said second conductive film;
- and
- a control gate electrode formed on said insulating film, wherein the second conductive film covers the first conductive film.
A method of manufacturing a nonvolatile semiconductor memory device comprising the steps of:
- forming a mask film including a first conductive film on a main surface of a semiconductor substrate;
- etching said semiconductor substrate masked with said mask film to form a trench for element isolation;
- forming a first insulating film covering said trench and said mask film;
- reducing the thickness of said first insulating film to expose said mask film;
- reducing the thickness of said mask film to expose said first conductive film and form a convexity projecting upward beyond an upper surface of said first conductive film at said first insulating film;
- forming a second conductive film located on said convexity to form an upward wall at said second conductive film;
- removing said second conductive film located on said convexity to form an upward wall at said second conductive film, such that the second conductive film covers the first conductive film;
- forming successively a second insulating film and a third conductive film covering said upward wall;
- and
- patterning said third conductive film, said second insulating film, said second conductive film and said first conductive film to form a floating gate electrode and a control gate electrode.
Dependencies are inferred from the claim text.