prevent disturbing non selected memory cells if a pre charging voltage of the non selected sub wordline can be controlled in response to write operations versus read operations power consumption of memory device can be further reduced the memory device 800 of fig8 includes a pre charging part 810 a pre charge voltage selector or voltage switching part 820 and a main wordline driver 830 thus the memory device 800 differs from the memory device 600 of fig6 in that it has the voltage switching part 820 the voltage switching part 820 includes a first switch so responsive to a write signal wr and a second switch s 1 responsive to a read signal rd or a standby signal sty the first switch so supplies a first boosting voltage vpp_wr to a main wordline driver and to the pre charging part 810 during a write operation the second switch s 1 supplies a second boosting voltage vpp_rd to the main wordline driver and to the pre charging part 810 during a read operation here vpp_wr is larger than vpp_rd thus because the memory device 800 uses vpp_wr and vpp_rd selectively according to whether a write operation or a read operation is executed power consumption can be further reduced for example the variable resistive memory device 600 of fig6 can be modified to include a pre charge voltage selector in signal communication with the sub wordline pre charging switch the pre charge voltage selector having a first selector switch in signal communication with a first voltage greater than a.