Carbon nanotube (CNT) growth on HfO₂ is reported for the first time. The process uses a combination of Ge and Fe nanoparticles and achieves an increase in CNT density from 0.15 to 6.2 µm length/µm² compared with Fe nanoparticles alone. The synthesized CNTs are assessed by the fabrication of back-gate CNT field-effect transistors with Al source/drain contacts for nano-sensor applications. The devices exhibit excellent p-type behavior with an I _on/I _off ratio of 10⁵ and a steep sub-threshold slope of 130 mV/dec.