Semiconductor memory device including initialization signal generation circuit

An initialization signal generation circuit includes: an initialization signal output unit configured to generate an initialization signal which is enabled during at least a portion of an auto refresh operation period of the initialization mode, in response to a flag signal; a refresh signal generation unit configured to generate a preliminary refresh signal and a refresh counting signal having the same period as the auto refresh signal in response to the flag signal and an auto refresh signal; and a counter unit configured to count a counting signal in response to the refresh counting signal and generate a counting initialization signal, which is delayed by at least a pulse width of the refresh counting signal, after a time point where a combination of the counting signal becomes a preset combination.