Acoustic wave element and acoustic wave device using same

摘要

A SAW element has a substrate; an IDT electrode located on an upper surface of the substrate and comprises Al or an alloy containing Al; a first film located on an upper surface of the IDT electrode; and a protective layer which covers the IDT electrode provided with the first film and the portion of the substrate exposed from the IDT electrode, which has a thickness from the upper surface of the substrate larger than a total thickness of the IDT electrode and first film, and which contains a silicon oxide. The first film contains a material which has a larger acoustic impedance than the material (Al or the alloy containing Al) of the IDT electrode and the silicon oxide and which has a slower propagation velocity of an acoustic wave than the material of the IDT electrode and the silicon oxide.

主权项

1. An acoustic wave element, comprising:
a piezoelectric substrate; an electrode which is located on an upper surface of the piezoelectric substrate and which contains Al as a major component; a first film which is located on an upper surface of the electrode; and an insulation layer which covers the first film and a portion of the piezoelectric substrate which is exposed from the electrode, which has a thickness from the upper surface of the piezoelectric substrate which is larger than a total thickness of the electrode and the first film, and which contains a silicon oxide as a major component, wherein the first film contains as a major component a material which has a larger acoustic impedance than a material of the electrode and a material of the insulation layer and which has a slower propagation velocity of an acoustic wave than the material of the electrode and the material of the insulation layer, and wherein a normalized thickness t/λ of the first film is within a range of a following equation (A):
t0/λ≦t/λ≦T/λ−0.1   equation (A) where T/λ is a normalized thickness of the insulation layer, “t” is a thickness of the first film, T is a thickness of the insulation layer, λ is a wavelength of the acoustic wave, and t0 is a thickness of the first film where a frequency of an upper end of a stop-band coincides with an antiresonance frequency.