Patent ID: 7759174

Claim:
A method of manufacturing a semiconductor device comprising: a substrate including a semiconductor and an electrically rewritable semiconductor memory provided on the substrate, the manufacturing method comprising: forming a trench on the surface of the substrate; forming first and second insulating films respectively on bottom and side surfaces of the trench; forming a charge storage layer, at least a part of the charge storage layer being provided in the trench, and an area of the lower surface of the charge storage layer being smaller than an area of the upper surface of the charge storage layer; forming a third insulating film on the charge storage layer; and forming a control gate electrode on the third insulating film, wherein the forming of the trench comprises forming a fourth insulating film on the substrate, and forming a trench that penetrates the fourth insulating film and reaches substantially a halfway depth of the substrate, and wherein the forming of the first and second insulating films comprises forming an insulating film on the bottom surface and side surface of the trench, wherein the side surface of the trench includes sidewalls of the substrate and sidewalls of the fourth insulating film within the trench, selectively removing the insulating film from the bottom surface of the trench to expose the substrate while retaining at least a portion of the insulating film on the side surface of the trench as the second insulating film, and forming the first insulating film on the exposed substrate at the bottom surface of the trench by oxidation.