An integrated circuit device is provided. The integrated circuit device may include a central processing unit (CPU) configured to operate in one of a plurality of modes and a wake-up control circuit configured to control the CPU. The wake-up control circuit may include a clock generator configured to generate an internal clock signal, a multiplexer configured to select a signal from among an external signal and the internal clock signal and to provide the CPU with the selected signal as an operating clock signal, and a controller configured to control the CPU and the clock generator based on the external signal.