US Patent 7582928 Nonvolatile semiconductor memory device and its manufacturing method

A non-volatile semiconductor memory device, which is intended to prevent data destruction by movements of electric charges between floating gates and thereby improve the reliability, includes element isolation/insulation films buried into a silicon substrate to isolate stripe-shaped element-forming regions. Formed on the substrate area floating gate via a first gate insulating film and further a control gate via a second gate insulating film. Source and drain diffusion layers are formed in self-alignment with control gates. The second gate insulating film on the floating gate is divided and separated together with the floating gate by slits above the element isolation/insulation films into discrete portions of individual memory cells.