| 摘要 |
In a surface acoustic wave device comprising an inter-digital electrode on a surface of a substrate wherein said substrate is a langasite single crystal belonging to a point group 32, a combination of a cut angle of the substrate out of the single crystal and-a propagation direction of surface acoustic waves is optimized. This makes it possible to achieve a surface acoustic wave device comprising a substrate having a temperature coefficient of SAW velocity, TCV, the absolute value of which is small, a large electromechanical coupling factor k2, and low SAW velocity. It is thus possible to achieve a filter device which is improved in terms of temperature stability, has a wide passband, and is reduced in size, especially an intermediate-frequency surface acoustic wave filter having improved characteristics best-fitted for mobile communication terminal equipment.
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