Implantable thermoelectric generators hold significant promise as an alternative or supplementary energy source for implantable medical devices, but their performance is constrained by spatial limitations within implants and relies heavily on design optimization. In this study, an optimized thermoelectric generator featuring high aspect ratio thermolegs (0.5 × 0.5 × 4 mm³) is presented, which achieves a remarkable power output of 110 µW with a simulated temperature difference (3 K) in an implantation scenario. This achievement is realized through the use of a removable assembly rig during the soldering process, streamlining the fabrication process. Furthermore, the integration of a boost converter within the thermoelectric generator results in a voltage output of 2.5 V, addressing the voltage requirements of active implants. These findings highlight the potential that implantable thermoelectric generators can be used as a reliable, quiet and self-sufficient power source for implantable medical devices.