Current trend towards miniaturization of micro electro-mechanical systems (MEMS) is leading to device featuring mechanical parts whose size are comparable to the morphology-induced length-scale of the of the polysilicon films they are made of. The device response to the external stimuli thus turns out to be affected more by scattering. We recently proposed an on-chip testing device, specifically designed to enhance such a scattering that can be caught by allowing for the morphology-affected mechanical properties of the silicon films and for etch defects induced by the micro-fabrication process. In this work, we discuss a stochastic framework allowing for the local fluctuations of the stiffness and of the etch-affected geometry of the silico...