A memory cell array includes a NAND string formed of a plurality of memory cells coupled in series between a string selection transistor and a ground selection transistor. The string selection transistor controls an electrical connection between the NAND string and a bit line based on a string selection voltage in a read operation. A row selection circuit is coupled to the memory cell array through a string selection line, ground selection line and a plurality of word lines. The row selection circuit selects a word line which is coupled to the read memory cell among the plurality of word lines based on a row address signal and a read voltage in a read operation. A voltage generation circuit generates the string selection voltage and the read voltage.