An internal voltage generator of a semiconductor memory device controls generating an internal voltage according to an increase of the internal voltage during an active mode, to thereby decrease current consumption. The internal voltage generator of a semiconductor memory device includes a voltage sensor, a plurality of first control units, a plurality of second control units, and a plurality of voltage drivers. The voltage sensor detects an internal voltage. The plurality of first control units generate a plurality of internal control signals according to the voltage level of an output of the voltage sensor. The plurality of second control units generate a plurality of driver control signals in response to the plurality of internal control signals. The plurality of voltage drivers are turned on/off in response to the plurality of driver control signals.