Embodiments of the invention provide a column address strobe (CAS) latency circuit that generates a stable latency signal in a high-speed semiconductor memory device, and a semiconductor memory device including the CAS latency circuit. The CAS latency circuit may include an internal read command signal generator and a latency clock generator coupled to a latency signal generator. In an embodiment of the invention, the latency signal generator outputs a stable latency signal by shifting an internal read signal output from the internal read command signal generator based on latency control clocks output from the latency clock generator.