Abstract – We demonstrate a microbump flip-chip integrated 14nm-FinFET CMOS-Silicon Photonics (SiPh) technology platform enabling ultra-low power Optical I/O transceivers with 1.6Tb/s/mm² bandwidth density. The transmitter combines a differential FinFET driver with a Si ring modulator, enabling 40Gb/s NRZ optical modulation at 154fJ/bit dynamic power consumption in a 0.015mm² footprint. The receiver combines a FinFET trans-impedance amplifier (TIA) with a Ge photodiode, enabling 40Gb/s NRZ photodetection with -10.3dBm sensitivity at 75fJ/bit power consumption, in a 0.01mm² footprint. High-quality data transmission and reception is demonstrated in a loop-back experiment at 1330nm wavelength over standard single mode fiber (SMF) with 2dB link margin. Finally, a 4×40Gb/s, 0.1mm² wavelength-division multiplexing (WDM) transmitter with integrated thermal control is demonstrated, enabling Optical I/O scaling substantially beyond 100Gb/s per fiber.