We demonstrate that fine-pitch TSV technology can be exploited to fabricate micro-inductors on high resistivity substrate, with record-high inductance per area and preserving their performance at GHz frequencies. We report an extensive experimental study on the effects of dimensional scaling and passive device density on RF performance of out-of-plane inductors exploiting W-based TSVs, with pitches down to 10 µm. We show wideband RF inductors with an unprecedented combination of a quality factor peak of 7.8 at 13 GHz, self-resonance frequency of 29.2 GHz, and inductance density of 124.4 nH/mm2. The reported technology also includes low loss interconnects, fixed capacitors and LC tanks, design to serving high performance 3D-integrated RF functionalities.