US Patent 8354706 Semiconductor memory device

A semiconductor memory device according to an embodiment of the present invention includes a substrate, a first gate insulator formed on the substrate and serving as an F-N (Fowler-Nordheim) tunneling film, a first floating gate formed on the first gate insulator, a second gate insulator formed on the first floating gate and serving as an F-N tunneling film, a second floating gate formed on the second gate insulator, an intergate insulator formed on the second floating gate and serving as a charge blocking film, and a control gate formed on the intergate insulator, at least one of the first and second floating gates including a metal layer.