| 摘要 |
To provide a boundary acoustic wave device that efficiently confines the vibrational energy of boundary acoustic waves and exhibits a high electromechanical coupling coefficient, and is consequently not affected by higher-order modes. The boundary acoustic wave device includes a first medium 11 having piezoelectric characteristics, a non-electroconductive second medium 12, and a third medium 13 through which slow transverse waves propagate at a lower acoustic velocity than slow transverse waves propagating through the first and second media 11 and 12. The first medium 11, the third medium 13, and the second medium 12 are stacked in that order. An IDT 14 is disposed between the first medium 11 and the third medium 13. The IDT 14 includes a metal layer made of a metal having a density Á in the range of 3000 to 21500 kg/m 3 . The IDT 14 has electrode fingers at a pitch of » and has a thickness H1 satisfying the relationship 0.006» ‰ H1 ‰ 0.2», and the third medium 13 has a thickness H2 satisfying the relationship H1 < H2 ‰ 0.7». |
