1. A method of efficiently managing a memory cell array by using a partial segment activation mode, wherein the memory cell array is divided into a plurality of segments as units, and each of a plurality of word lines included in each of the plurality of segments is driven by a corresponding sub-word line driver, comprising the steps of: activating a main word line by information on the remaining bits except information on some bits of a row address; activating only sub-word lines included in desired segments by decoding a combination of the information on some bits of the row address and information on some bits of a column address; and operating sense amplifiers each connected with an associated one of the activated sub-word lines.