  Dielectric nanoresonators have been shown to circumvent the heavy optical
losses associated with plasmonic devices, however they suffer from less
confined resonances. By constructing a hybrid system of both dielectric and
metallic materials, one can retain the low losses of dielectric resonances,
whilst gaining additional control over the tuning of the modes with the metal,
and achieving stronger mode confinement. In particular, multi-layered van der
Waals materials are emerging as promising candidates for integration with
metals owing to their weak attractive forces, which enable deposition onto such
substrates without the requirement of lattice matching. Here we use layered,
high refractive index WS$_2$ exfoliated on gold, to fabricate and optically
characterize a hybrid nanoantenna-on-gold system. We experimentally observe a
hybridization of Mie resonances, Fabry-P\'erot modes, and surface
plasmon-polaritons launched from the nanoantennas into the substrate. We
achieve experimental quality factors of Mie-plasmonic modes of up to 20 times
that of Mie resonances in nanoantennas on silica, and observe signatures of a
supercavity mode with a Q factor of 263 $\pm$ 28, resulting from strong mode
coupling between a higher-order anapole and Fabry-P\'erot-plasmonic mode. We
further simulate WS$_2$ nanoantennas on gold with an hBN spacer, resulting in
calculated electric field enhancements exceeding 2600, and a Purcell factor of
713. Our results demonstrate dramatic changes in the optical response of
dielectric nanophotonic structures placed on gold, opening new possibilities
for nanophotonics and sensing with simple-to-fabricate devices.
