  Two major challenges in the development of optomechanical devices are
achieving a low mechanical and optical loss rate and vibration isolation from
the environment. We address both issues by fabricating trampoline resonators
made from low pressure chemical vapor deposition (LPCVD) Si$_3$N$_4$ with a
distributed bragg reflector (DBR) mirror. We design a nested double resonator
structure with 80 dB of mechanical isolation from the mounting surface at the
inner resonator frequency, and we demonstrate up to 45 dB of isolation at lower
frequencies in agreement with the design. We reliably fabricate devices with
mechanical quality factors of around 400,000 at room temperature. In addition
these devices were used to form optical cavities with finesse up to 181,000
$\pm$ 1,000. These promising parameters will enable experiments in the quantum
regime with macroscopic mechanical resonators.
