| 摘要 |
PROBLEM TO BE SOLVED: To provide a thin-film surface acoustic wave filter with less propagation loss. SOLUTION: In a thin-film surface-acoustic wave filter, an artificial diamond film is formed to a surface of a board, and a piezoelectric thin film is formed on the surface of the artificial diamond film via an interdigital electrode, while the surface roughness Ra is selected to be 20nm or below. In this case, a nitrogen or argon ion-implantation layer whose depth is 0.01-2μm and whose injection atom concentration is 1×10<11> -1×10<21> atoms/cm<3> , measured at the ion- implantation face of the artificial diamond film to a junction surface of the interdigital electrode and the piezoelectric thin film of the artificial diamond film.
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