Acoustic wave device, high frequency front end circuit, and communication apparatus
An acoustic wave device includes a piezoelectric substrate made of LiNbO 3 , and a dielectric film provided on the piezoelectric substrate to cover first and second IDT electrodes on the piezoelectric substrate. The first and second IDT electrodes include main electrode layers. When wave lengths determined by electrode finger pitches of the first and second IDT electrodes are λ 1 and λ 2 , respectively, the average value thereof is λ 0 , λ 1 /λ 0 =1+X, and λ 2 /λ 0 =1−X, a relationship of 0.05≤X≤0.65 is satisfied. The wavelength λ 1 is the longest, and the wavelength λ 2 is the shortest. In Euler angles (φ, θ, ψ) of the piezoelectric substrate, φ is 0°±5°, ψ is 0°±10°, and θ satisfies Expression 1, wherein a relationship of B 1 <T×r≤0.10λ 0 and B 2 <T×r≤0.10λ 0 are satisfied.
1. A high frequency front end circuit comprising:
a power amplifier; and
an acoustic wave device including:
a piezoelectric substrate made of LiNbO 3 (lithium niobate);
a plurality of interdigital transducer (IDT) electrodes provided on the piezoelectric substrate and including a first IDT electrode and a second IDT electrode; and
a dielectric film provided on the piezoelectric substrate to cover the plurality of IDT electrodes; wherein
the dielectric film includes silicon oxide as a main ingredient;
the first IDT electrode and the second IDT electrode include main electrode layers;
a film thickness and a material of the main electrode layer of the first IDT electrode are the same or substantially the same as a film thickness and a material of the main electrode layer of the second IDT electrode;
a film thickness of a portion of the dielectric layer provided on the first IDT electrode is equal or substantially equal to a film thickness of a portion of the dielectric film provided on the second IDT electrode;
a plurality of band pass filters belonging to communication bands of different pass bands are provided on the piezoelectric substrate;
an antenna terminal to be connected to an antenna is provided on the piezoelectric substrate;
the plurality of band pass filters are commonly connected to the antenna terminal to define a composite filter; and
among the plurality of IDT electrodes, a wave length λ 1 determined by an electrode finger pitch of the first IDT electrode is the longest, and a wave length λ 2 determined by an electrode finger pitch of the second IDT electrode is the shortest.
2. The high frequency front end circuit according to claim 1 , wherein the first IDT electrode and the second IDT electrode are included in different band pass filters among the plurality of band pass filters.
3. The high frequency front end circuit according to claim 1 , wherein
the first IDT electrode includes:
a first busbar and a second busbar that are opposing each other;
a plurality of first electrode fingers connected to the first busbar; and
a plurality of second electrode fingers connected to the second busbar; and
the plurality of first electrode fingers and the plurality of second electrode fingers are interleaved with each other.