US Patent 7256443 Semiconductor memory and method of manufacturing the same

A semiconductor memory has plural cell transistors that are arranged in a matrix. The cell transistor comprises a silicon substrate, a control gate, a pair of electrically isolated floating gates. Plural projections are formed in the P type silicon substrate, and a pair of N type diffusion regions as the source and the drain is formed in both sides of the projection. The control gate faces the projection via a fourth insulation layer. The side surface of the floating gates faces the side surfaces of the projection via a first insulation layer, and faces the control gate via a third insulation layer. The floating gate faces the diffusion region via the first insulation layer.