A refresh signal generator generates an internal refresh signal to conduct a refresh with an interval controlled based on PVT fluctuations. The refresh signal generator includes a temperature sensing unit for sensing an internal temperature and activating a corresponding signal of a plurality of temperature sensing signals in response to a temperature sense driving signal, a power supply selecting unit for driving a driving voltage supply terminal to one of different voltage levels according to the plurality of temperature sensing signals, and an internal refresh signal generating unit for receiving a driving voltage from the power supply selecting unit and producing internal refresh signals at a constant interval.