| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface acoustic wave device which is free from deterioration in its characteristic and has high reliability by providing an exciting electrode, etc., on a piezoelectric substrate to generate a surface acoustic wave and laminating a protective film having a surface acoustic wave speed higher than the piezoelectric substrate and having a specific relative resistance value/ film thickness on the exciting electrode. SOLUTION: A metallic exciting electrode 2 and a reflector electrode 3 are provided on a piezoelectric substrate 1, and a protective film 4 is formed at the areas of both electrodes 2 and 3. The substrate 1 uses a lithium tantalate material and the film 4 uses a such material as silicon, having a higher surface acoustic wave speed than the substrate 1. Thus, the electrode pitch is decided with a larger degree of freedom and production of the electrode 2 is facilitated. Furthermore, the ratio between the relative resistance value and the thickness is set at 10<9> to 10<13>Ωfor the material of the film 4. Thereby, the extra electric charge flows through the film 4 to relax the unevenness of a charge density distribution that is caused among electrode fingers of the electrode 2, etc., by the pyroelectricity of the substrate 1.
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