A micromechanical resonator with high quality factor and small size at 12.12 GHz has been designed and relevant measured data have been obtained. The dimensions of hybrid cavity structure filled in Rogers Duroid (εr=10.8) is 8.2mm×4.4mm×1mm. Electromagnetic energy is coupled into the cavity from input and output microstrip lines with characteristic impedance of 50 ohm via slots. The hybrid cavity resonator was fabricated by standard silicon micromachining process and bolding technique. Theoretical and measured resonance frequency of TE101 mode is 12.12 GHz and 11.84 GHz respectively. The unloaded Q factor is 303. The errors between theoretical and measured results were analyzed.