A semiconductor memory device and a control signal generating method thereof. The semiconductor memory device may include a voltage range detector configured to generate a voltage detecting signal corresponding to a range of a level of an external power voltage. A control signal generating portion may be used to generate a control signal corresponding to the range of the level of the external power voltage responsive to the voltage detecting signal. As a result, the semiconductor memory device can perform an operation for satisfying an access time characteristic according to a specification responsive to the control signal.