The Finite Element Method (FEM) simulations activity at CNR-IMM supports the design of MEMS devices for low power consumption and Energy Harvesting applications. Coupled physics phenomena are modelled and solved by using Comsol Multiphysics®. Coupled thermal and electrical analysis allows to maximize the performance of thermoelectric generators (TEGs), based on planar and vertical thermopiles, by optimizing the design of modules and the package of devices. FEM simulations are also implemented to evaluate the deflection and stress distribution in different-shaped floating membranes of capacitive pressure sensors, where small or large deformations in the model can be considered. About the piezoelectric devices, the piezoelectricity is combined with solid mechanics and electrostatics equations and physics features for a comprehensive modelling of generation behaviour. Piezoelectric coupling can be on stress-charge or strain-charge form. FEM analysis is used to study low temperature plasmas and to model dielectric barrier discharge in embedded system of sensor-DBD actuator for detection and control of flow separation in aeronautical applications.