| 摘要 |
A boundary acoustic wave device efficiently traps 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 having piezoelectric characteristics, a non-electroconductive second medium, and a third medium through which slow transverse waves propagate at a lower acoustic velocity than slow transverse waves propagating through the first and second media. The first medium, the third medium, and the second medium are stacked in that order. An IDT is disposed between the first medium and the third medium. The IDT includes a metal layer made of a metal having a density rho in the range of about 3000 kg/m3 to about 21500 kg/m3. The IDT has electrode fingers arranged at a pitch of lambda and has a thickness H1 satisfying the relationship 0.006lambda<=H1<=0.2lambda, and the third medium has a thickness H2 satisfying the relationship H1<H2<=0.7lambda.
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