A circuit module for a digital television receiver is formed by multi-layering a decoder LSI including a CPU and a decoder, a decoder layer substrate including a CA interface circuit, a demodulation function layer substrate including a demodulator, and an extension function layer substrate including a communication controller. The demodulation function layer substrate and the extension function layer substrate can be selectively multi-layered to the decoder layer substrate in response to a broadcasting system of a digital television signal or a type of a CA module.