The working principle of an electromechanical resonator for mass sensing applications is based on monitoring the characteristic resonance frequency downshift due to the particles attachment on the surface of the device. Solid-Gap Vibrating-Body Field Effect Transistor (VB-FET) resonators offer an interesting solution for extreme biomass sensing due to their high motional current at resonance, their compatibility with Complementary Metal-Oxide-Semiconductor (CMOS) circuits, high reproducibility of characteristics and the possibility to have exploitable values of the quality factor (Q-factor) in air and liquid operation. In this work a detailed micromechanical analysis of VB-FET disk resonators is carried out, considering geometrical design parameters, geometrical variability, motional resistance for air and solid-gaps, Q-factor and variable particle-resonator sensing cases, permitting quantitative discussions on their suitability for biosensing.