PURPOSE: To facilitate the compatibility with a radio frequency surface acoustic wave by a method wherein a multilayer structure piezoelectric device substrate on which a piezoelectric IV-V compound film and a piezoelectric composite oxide film are formed is employed to make the speed of the elastic surface wave, an electromechanical coupling constant, etc. have specific values.

CONSTITUTION: A piezoelectric IV-V compound film is formed on a substrate and, further, a composite oxide film which is made of at least 3 types of elements is formed on it. The substrate is made of sapphire or glass. An aluminum nitride film or a GaAs film is used as the piezoelectric IV-V compound film. A lithium niobate film is used as the composite oxide film. The speed of the surface acoustic wave, the electromechanical coupling constant and the absolute value of the temperature coefficient of the central frequency of the piezoelectric device substrate are predetermined to be not less than 5000m/s, not less than 1% and not larger than 30ppm/°C respectively. For that purpose, the thickness of the piezoelectric TV-V compound film is predetermined to be 0.001-15μm and the thickness of the piezoelectric composite oxide film is predetermined to be 0.01-10μm.