PURPOSE: To form an electrode structure of a thin zinc oxide film which has practically sufficient and stable characteristics by interposing a Ta layer as a preventing layer for diffusion of Cr and Ti between the thin zinc oxide film and a Cr-Au or Ti-Au electrode.

CONSTITUTION: The thin zinc oxide film 12 is formed on an oscillator 11, a Ta layer 13 is formed thereupon to an about 100 thickness, and the Cr-Au or Ti-Au electrode 14 is formed thereupon. Said Ta layer 13 is formed by an electron beam, sputtering, ion beam, or resistance heat vapor-depositing method, etc. Consequently, the thin zinc oxide film with practically sufficient characteristics is obtained. Further, the result of a life test for the high-temperature load lift of the thin zinc oxide film shows small variation in oscillation frequency and IR, small variation in the value of Ro, and high reliability.