| 摘要 |
An elastic boundary wave device having the reduced maximum quantity of insertion loss at a specific frequency of unnecessary response. The device includes a piezoelectric substrate (16) having piezoelectric properties, interdigitated electrodes (14a,14b) formed on the piezoelectric substrate, a first medium (17) formed on the substrate to cover the electrodes, and a second medium (18) formed on the first medium. The interdigitated electrode has a plurality of electrode digits (13a,13b) and a bus bar (12a) for connecting ends of the plurality of digits. A third medium (19a) formed on the first medium is provided. The second and third media are in contact with the first medium. The first, second and third media are constituted of different materials from one another. A ratio in length of a part having the third medium formed with respect to a length of a propagation path of elastic boundary waves on a cross section vertical to the longitudinal direction of the electrode digit differs in the longitudinal direction of the digit.
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