Aluminum nitride (AlN) has emerged as an excellent material for a wide range of MEMS applications. This presentation will cover key aspects of AlN thin-film growth, material characterization, device design, fabrication and device characterization. A two-step growth technique combining MOCVD and sputtering is demonstrated to realize thick, high-quality AlN films on Si (111) substrate. These films are utilized in a novel cantilever geometry with an extended tip mass to achieve low resonant frequencies without increasing device footprint, while enhancing charge output. An AI/ML based optimization using Gaussian Process Regression and Genetic Algorithm is employed to design optimal cantilevers for applications including cochlear implants, real-time spectral analyzer, and high-bandwidth accelerometer. A multi-device fabrication platform on Si/SOI (111) is developed for fabrication of these devices. Initial characterization results are presented for fabricated devices viz. a cantilever array and a high-bandwidth accelerometer. Finally, a novel method for the direct measurement of spontaneous polarization in pyroelectric thin films using a MEMS TPoS device is proposed.