1. Field of the Invention
The present invention relates to a piezoelectric device using a piezoelectric material.
2. Related Background Art
Recently, practical application of piezoelectric devices using thin film piezoelectric materials is spreading, in place of bulk piezoelectric materials. Examples of such application include gyro sensors, shock sensors, microphones, etc. making use of the piezoelectric effect to convert a force exerted on a piezoelectric film to a voltage, or actuators, ink jet heads, speakers, buzzers, resonators, etc. making use of the inverse piezoelectric effect to deform a piezoelectric film with application of voltage thereto.
Reduction in thickness of the piezoelectric material will enable reduction in scale of the piezoelectric device to expand fields of application. Since a large number of piezoelectric devices can be manufactured together on a substrate, mass productivity must increase. Furthermore, there are many advantages in terms of performance, e.g., improvement in sensitivity when the piezoelectric film is used in a sensor. However, external stress from other films to the piezoelectric film and internal stress of the piezoelectric film itself will bring about more influence on the piezoelectric characteristics than in the case of the bulk materials, and for this reason the piezoelectric thin film requires a stress control technology different from that for the bulk materials. Therefore, a control method of the piezoelectric characteristics with focus on control of thermal stress applied to interfaces of the piezoelectric film becomes an important factor in design of the piezoelectric device.