Piezoelectric MEMS Energy Harvester

Hi,
I'm using COMSOL MEMS Module and trying to compute eigen frequency and frequency response of the MEMS energy harvester design. My design have non-linear cantilever clamped at both ends and proof mass at the center of the beam. The active piezoelectric layer is AlN material of thickness 400nm and other elastic material layers, electrodes are of around or less than 200nm thickness.

I facing difficulty in meshing these thin layers. I have tried swept, free triangular boundary layer meshes but ended up with errors and problems. Please help me and guide me as Im a beginner to COMSOL FEA.

Thanks a lot!