Silicon nitride films were deposited by hot-wire chemical vapor deposition processes (HW-CVD). The films reveal a morphological structure very similar to nitrides formed in low pressure CVD (LP-CVD) or plasma enhanced CVD (PE-CVD) processes. The electrical breakdown voltages, however, are much smaller for HW- than PE- or LPCVD films. The deposition in holes for isolation purpose in “through silicon vias” (TSV) technologies in combination with optical devices, which require very low temperatures (<200 °C), have been investigated. They reveal sufficiently good properties for the planned applications.