Patent ID: 7394336

Claim:
An elastic boundary wave apparatus comprising: a first medium; a second medium stacked on the first medium; and a plurality of electrodes arranged in a boundary between the first and second media; wherein a filter and/or a resonator, and an electrostatic capacitor that is electrically connected to the filter and/or the resonator are defined by the plurality of electrodes; the filter and/or the resonator each include an IDT electrode; the electrostatic capacitor includes a comb-shaped capacitor electrode; and when a period of the electrode fingers of the IDT is denoted as λm, a sound velocity of an elastic boundary wave in the IDT is denoted as Vm, a period of electrode fingers of the comb-shaped capacitor electrode is denoted as λc, and a sound velocity of a transverse wave having a lower sound velocity among the lower sound velocities of transverse waves through the first and second media in the normal direction of the electrode fingers of the comb-shaped capacitor electrode is denoted as Vc, a relationship Vm/λm<Vc/λc is satisfied.