A nonvolatile semiconductor memory device includes a semiconductor substrate having a plurality of active regions separately formed by a plurality of trenches formed in a surface of the substrate at predetermined intervals, a first gate insulating film formed on an upper surface of the substrate corresponding to each active region, a gate electrode of a memory cell transistor formed by depositing an electrical charge storage layer formed on an upper surface of the gate insulating film, a second gate insulating film and a control gate insulating film sequentially, an element isolation insulating film buried in each trench and formed from a coating type oxide film, and an insulating film formed inside each trench on a boundary between the semiconductor substrate and the element isolation insulating film, the insulating film containing nontransition metal atoms and having a film thickness not more than 5 Å.