In a boosted voltage generating circuit of a semiconductor memory device, an active kicker drive signal generating circuit generates an active kicker drive signal having a first pulse duration in response to a row active command, and generates the active kicker drive signal having a second pulse duration in response to a refresh command. An active kicker circuit is responsive to the active kicker drive signal to generate the boosted voltage. The second pulse duration may be greater than the first pulse duration, which makes it possible to improve the pumping efficiency of the boosted voltage in a refresh operation.