A DLL (Delay Locked Loop) clock signal generating circuit includes a duty correction buffer for receiving a first clock signal and a second clock signal, producing a first internal clock signal and a second internal clock signal, and correcting duty ratios of the first and second internal clock signals based on a reference signal which is controlled by a duty ratio of the first internal clock signal, and an edge trigger unit for a DLL clock signal which has a first level when the first internal clock signal is activated and which has a second level when the second internal clock signal is activated.