An internal voltage generator of a semiconductor device includes a charge pumping unit for performing a charge pumping operation on the basis of the voltage level of a reference voltage to generate a charge pumped voltage having a voltage level higher than the external power supply voltage; and an internal voltage generating unit for performing a charge pumping operation on the basis of an internal voltage level that is linear with respect to a temperature change in a first temperature range to generate an internal voltage, and to perform a charge pumping operation on the basis of an internal voltage clamping level that is constant independent of a temperature change in a second temperature range to generate the internal voltage.