Piezoelectric materials generate an electric charge by applying force or generate a force by applying a voltage. Micro electro-mechanical systems (MEMS) devices that use piezoelectric materials as sensors and actuators are called as piezoelectric MEMS devices. The piezoelectric constant of PZT depends on the Zr/Ti ratio. The origin is that the crystal structure of PZT depends on the Zr/Ti ratio. The piezoelectric constant of a PZT thin film is greatly affected not only by its composition but also by its orientation. Most of the PZT thin films used in commercialized PZT-MEMS devices are formed by sol–gel or sputtering. The crystal orientation of PZT thin films is determined by the first film deposition. The chapter describes the fabrication process for piezoelectric MEMS cantilevers and optical scanners from silicon-on-insulator wafers on which PZT thin films are formed. Most of the PZT thin films for MEMS are polycrystalline ones.