NONVOLATILE SEMICONDUCTOR DEVICE AND METHOD OF MANUFACTURING NONVOLATILE SEMICONDUCTOR DEVICE

PROBLEM TO BE SOLVED: To provide a nonvolatile semiconductor device capable of ensuring the function of the nonvolatile semiconductor device and having suppressed variations in threshold voltage of a floating gate.SOLUTION: A nonvolatile semiconductor device comprises: a semiconductor substrate 11 having a primary surface; a first and second floating gates 15a and 15b formed apart from each other above the primary surface of the semiconductor substrate 11; a first and second control gates 12a and 12b above the first and second floating gates 15a and 15b; a first insulating film 32a formed above the first control gate 12a; a second insulating film 32b formed above the second control gate 12b so as to contact the first insulating film 32a; and a hollow portion 26a formed at least between the first floating gate 15a and the second floating gate 15b by contacting the first insulating film 32a and the second insulating film 32b.