Patent ID: 7876020

Claim:
A boundary acoustic wave device comprising: a piezoelectric substance; a dielectric substance stacked on the piezoelectric substance; and IDT electrodes arranged between the piezoelectric substance and the dielectric substance; wherein the piezoelectric substance has a negative temperature coefficient of frequency; the dielectric substance has a positive temperature coefficient of frequency; each of the IDT electrodes includes: a first conductive layer arranged on a side of the piezoelectric substance and composed of a metal with a relatively high density or an alloy primarily containing the metal; a second conductive layer arranged on a side of the first conductive layer adjacent to the dielectric substance and composed of a metal with a relatively low density or an alloy primarily containing the metal; and a third conductive layer arranged on a side of the second conductive layer adjacent to the dielectric substance and composed of a metal with a relatively high density or an alloy primarily containing the metal; wherein if thicknesses of the first, second, and third conductive layers are H 1 , H 2 , and H 3 , and a period of the IDT electrodes is λ, the following relationships are satisfied: 0.04 λ<H 1 +H 3<0.12λ H1>0.009λ, H3>0.022λ 0.05λ<H2<0.16λ.