Embodiments provide a control circuit and a semiconductor memory. The control circuit includes a bias switching circuit and a first logic gate circuit. The first logic gate circuit includes at least one target transistor. A substrate of one of the at least one target transistor is connected to an output terminal of the bias switching circuit. The first logic gate circuit has a first speed mode and a second speed mode. A transmission speed of the first speed mode is less than a transmission speed of the second speed mode. The bias switching circuit is configured to: receive a target signal, and output a target bias voltage, to increase a threshold voltage of the target threshold. The enabled state of the target signal represents that the first logic gate circuit is in the first speed mode.