Voltage generator and nonvolatile memory device including the same

A voltage generator includes a high voltage generator configured to include a plurality of pump circuits for generating various levels of a high voltage in response to clock signals, wherein the plurality of pump circuits are configured to receive enable signals corresponding to a level of voltage to be generated, where the enable signals are generated in response to internal operation signals. And a clock transfer circuit configured to generate a clock enable signal by comparing the high voltage and a reference voltage and to selectively provide the clock signals to each of the pump circuits in response to the clock enable signal and each of the enable signals.