Patent ID: 7095999

Claim:
A radio-communication semiconductor integrated circuit comprising: a low-noise amplification circuit receiving a signal and providing an amplified signal having a first frequency; a first mixer receiving the amplified signal and converting the amplified signal to a signal having a second frequency which is lower than the first frequency; a demodulator coupled to the first mixer and demodulating the signal having the second frequency; a modulator modulating a signal to be transmitted; and a second mixer coupled to the modulator and providing a signal having a third frequency in accordance with an output signal from the modulator, wherein the first mixer is formed in a first island area which is an area enclosed by an isolation band in a first semiconductor region which is disposed on a surface of a second semiconductor region via an isolation region, wherein the second mixer is formed in a second island area which is an area enclosed by an isolation band in the first semiconductor region, and wherein one of the first island area and the second island area includes a third semiconductor region to which a predetermined voltage is applied and which has a resistance lower than that of the one of the first island area and the second island area.