Patent ID: 8575017

Claim:
A method of manufacturing a non-volatile semiconductor memory device, comprising: forming a first insulating film on a semiconductor substrate; forming on the first insulating film a first electrode layer to be turned into floating gates; forming element isolation trenches extending from the first electrode layer into the semiconductor substrate to define element forming regions in the semiconductor substrate; forming a buried film in the element isolation trenches in the semiconductor substrate; forming a second insulating film on the first electrode layer and the buried film; forming on the second insulating film a second electrode layer to be turned into control gates; selectively removing the second electrode layer to form the control gates crossing the element forming regions and the element isolation trenches; selectively removing the second insulating film located between the control gates to expose the buried film between the control gates through a region from which the second insulating film is removed; and removing the buried film exposed between the control gates and the buried film located beneath the control gates after selectively removing the second insulating film; wherein air gaps are formed by removing the buried film located beneath the control gates.