A semiconductor system may include a controller and a semiconductor memory device. The controller may provide an external command, an external address and a first external clock. The controller may be configured to transmit a second external clock and receive a third external clock for receiving/transmitting external data. The semiconductor memory device may be configured to synchronize and receive the external address and the external command with the first external clock. The semiconductor memory device may be configured to synchronize and receive the external data with the second external clock. The semiconductor memory device may be configured to transmit the external data and the third external clock to the controller.