A semiconductor device includes an error check and scrub (ECS) command generation circuit and an ECS control circuit. The ECS command generation circuit generates an internal refresh command after generating an ECS command based on a refresh command and an idle signal. The ECS control circuit generates an ECS mode signal that is activated during an ECS operation based on the ECS command. The ECS control circuit also generates an ECS active command, an ECS read command, and an ECS write command for performing the ECS operation based on the ECS command.