This paper reports a fully implantable, MEMS-based, low-power, energy harvesting, next generation cochlear implant (CI). The implant includes multi-frequency piezoelectric transducers for sound detection and energy harvesting, rectification and signal conditioning electronics, and RF coil for fitting and external powering. These units have outstanding performances: multi-channel transducer can generate 50.7 mVpp (under 100 dB SPL) and recover the daily sound speech signals; signal conditioning IC consumes outstandingly low power (<500 µW) while converting outputs signals of the transducer to biphasic pulses; piezoelectric energy harvester has the highest power density (1.5 × 10 −3 W/cm 3 ) with generated 16.25 µW under 120 dB-A sound input; energy harvester IC, provides up to 500% more power compared to an ideal fullbridge rectifier.