A semiconductor memory device comprises a variable delay unit and a data trainer. The variable delay unit is configured to generate a write data signal by delaying a write data driving signal by different amounts of time depending on whether the semiconductor memory device is in a data training mode or a normal operating mode, and further configured to generate a read data driving signal by delaying a read data signal by different amounts of time in the data training mode and the normal operating mode. The data trainer is configured to be activated in the data training mode, and while activated, receive the write data signal, compare the write data signal with a predetermined write pattern, perform a data training mode operation, and output the read data signal with a predetermined read pattern.