Patent ID: 8629598

Claim:
A boundary acoustic wave device comprising: a piezoelectric substrate; a first medium layer made of a first dielectric material disposed on the piezoelectric substrate; a second medium layer disposed on an upper surface of the first medium layer, made of a second dielectric material having an acoustic velocity different from an acoustic velocity of the first dielectric material; and an IDT electrode arranged along an interface between the piezoelectric substrate and the first medium layer; wherein a value of at least one of a normalized thickness of the first medium layer, a duty of the IDT electrode, and a normalized thickness of the IDT electrode is set such that the boundary acoustic wave device satisfies a relationship Va>V 1 , where V 1 represents an acoustic velocity of a fast transverse bulk wave of the piezoelectric substrate, and Va represents an acoustic velocity of a higher-order mode boundary acoustic wave at an anti-resonance point, such that the higher-order mode boundary acoustic wave is leaked to the piezoelectric substrate.