A method of manufacturing a nonvolatile semiconductor memory device comprising: forming a trench in a silicon substrate; forming a silicon dioxide film along an internal surface of the trench of the silicon substrate; removing the silicon dioxide film formed on a bottom surface of the trench of the silicon substrate by an anisotropic etching process; and forming an ozone tetraethyl orthosilicate (O3-TEOS) film on an inner side of the silicon dioxide film by selectively depositing the O3-TEOS film on the bottom surface of the trench of the silicon substrate by a thermal CVD method.