| 摘要 |
PROBLEM TO BE SOLVED: To obtain a passband filter structure which improves a frequency characteristic and whose attenuation gradient outside a pass band is steep by constructing a bulk sound wave filter structure having a lattice structure in which two resonators have an area being different from that of the other two resonators and further using a sound wave mirror structure for sound interruption to simplify the mechanical structure of a filter structure. SOLUTION: This structure has bottom electrodes 110, upper part electrodes 120 and voltage layers 100 between the electrodes. Four voltage layers 100 being resonators can also form separated continuous layers or a single continuous layer. The area of a resonator is defined as overlapping areas of the electrodes 120 and 110 at substantially overlapping positions. The structure is provided with a 1st bulk sound wave resonator substantially having a 1st area, a 2nd bulk sound wave resonator substantially having the 1st area, a 3rd bulk sound wave resonator substantially having a 2nd area and a 4th bulk resonator substantially having the 2nd area.
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