the bit line overdrive circuit of the present invention comprises a vblh potential generation circuit generating a bit line final potential relative to a vblh power supply line for driving a sense amplifier , a charge adjusting capacitance c , a transistor for supplying an overdrive potential to the vblh power supply line , and a transistor for connecting a pcs node to the vblh power supply line . the charge pre - charged from the overdrive potential to the vblh power supply line is shared among the capacitance of the above - noted circuit elements connected to the vblh power supply line , the bit line capacitance , and the capacitance of a cell capacitor so as to form a vblh power supply of a substantially one system , thereby avoiding the generation of a power supply noise caused by the power supply switching .