This paper presents an integrated 140 GHz receiver in 65 nm CMOS including a power detector for high-bandwidth and power-efficient communication and radar applications. The mm-wave power detector utilizes a self-mixer scheme by the use of an NMOS transistor fed to a simple RC low-pass filter. Measured result shows that it can operate in a wide-band frequency range of 134-158 GHz and the proposed receiver occupies a small core area of 220 μm×220 μm. To realize the demodulated waveform and bit error rate (BER) measurements, we fabricated a prototype including an OOK modulator followed by the proposed receiver in a 65 nm CMOS process. The prototype successfully demonstrates a demodulated waveform and BER test at 11 Gb/s with a carrier frequency of 140 GHz. The measured BER is 2.1 × 10-4 at 11 Gb/s and less than 1 × 10-11, which is a limit of the BERT, at 8 Gb/s or less. Our OOK transceiver prototype can achieve low power, high isolation, and small die area with more design freedom and suitable for mm-wave D-band communication or radar systems.