A semiconductor device may include a syndrome generation circuit and a failure detection circuit. The syndrome generation circuit may generate a syndrome signal corresponding to a pattern of an output data signal. The failure detection circuit may detect the syndrome signal and sequentially store the syndrome signal to generate a first syndrome signal and a second syndrome signal if an error is detected from the syndrome signal. The failure detection circuit may generate a failure detection signal which is enabled if a logic level combination of the first syndrome signal is different from a logic level combination of the second syndrome signal.