We report on harsh-environment-compatible Pt-TSVs forming ohmic contacts with a highly doped bulk silicon. They were developed as a part of a Single Wall Carbone NanoTube (SWCNT) resonator device with 3D-packaging. The fundamental properties of the TSVs, experimentally obtained with bulk Si instead of the real working device, are presented. Our concept for the device fabrication is “via first”, followed by the nanodevice fabrication. As such, first ohmic contacts on silicon has been studied to be compatible with several harsh post-processing steps, including high temperature treatments—up to 850°C in air—and concentrated HF-based release steps. Then TSVs withstanding the aforesaid conditions have been developed. These interconnects are also of interest for MEMS devices operating at high temperature.