The large amplitude non-linear vibratory behavior of a stratified circular plate with a piezoelectric patch is addressed in this study. The goal is to build an efficient model of a resonating MEMS (Micro Electro Mechanical System) bio-sensor whose function is to detect in real-time the presence of a given molecule (the so called target molecule) in a liquid medium. This study introduces the plate equations of motion, that includes the effects thermal-like prestresses, the piezo-electric material, its stratified structure with two annular regions and the geometrical non-linearities stemming from large deflections. Their resolution by an expansion onto the eigenmodes of the unstressed system gives the first insights in the buckling phenomena and the nonlinear vibrations.