Abstract: A memory device includes a memory cell array including normal memory cells arranged in a form of matrix, and a sense amplifier array including sense amplifiers each amplifying a signal output from each of the normal memory cells. Some of the sense amplifiers have different sizes so that they may have different sense capabilities depending on a layout location. The size is determined according to at least one of a channel length and a channel width of a MOS transistor included in each of the some sense amplifiers.