There is provided a semiconductor memory having a reduced power consumption in data access and a high access speed in a NAND cell array scheme in which a memory cell unit is constituted by cascade-connecting a plurality of memory cells with each other. A memory cell array is divided into a plurality of sub-arrays, and the divided sub-arrays are selectively activated, thereby decreasing the capacitances of the word lines, register word lines, bit lines, and the like which are charged/discharged in data access.