The memory cell transistor has a first cell site gate insulator, a first lower conductive layer on the first cell site gate insulator, a first inter-electrode dielectric on the first lower conductive layer, and a first upper conductive layer on the first inter-electrode dielectric. A select transistor has a second cell site gate insulator having a same thickness as the first cell site gate insulator, a second lower conductive layer on the second cell site gate insulator, a second inter-electrode dielectric on the second lower conductive layer, and a second upper conductive layer on the second inter-electrode dielectric. The peripheral transistor has a first peripheral site gate insulator having a thickness thinner than the first cell site gate insulator.