An operation method of a memory device includes sequentially receiving an active command and a precharge command from an external device, during a first time interval, applying a first activation voltage to a selected wordline in response to the active command, applying a second activation voltage to the selected wordline after the first time interval elapses from a first time point when the first active command is received, and applying a first deactivation voltage to the selected wordline in response to the precharge command. The second activation voltage is lower than the first activation voltage and is higher than the first deactivation voltage.