| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface acoustic wave device provided with a special electrode structure placed on a substrate having a natural single-phase unidirec tional transducer characteristic suitable for configuring a surface acoustic wave filter possible for miniaturization and a low loss. SOLUTION: The 2-terminal surface acoustic wave device the number of one reflector of which is reduced to 50 to 90% has a langasite structure, is made of an oxide single crystal consisting of at least lanthanum, gallium, and niobium. Substrates whose cut angle and propagation direction of a surface acoustic wave expressed in terms of the Euler angle representation (ϕ,θ,ψ) of (1) 90 deg.<=ϕ<100 deg., 145 deg.<=θ<=170 deg., 110 deg.<=ψ<=140 deg., (2) 100 deg.<=ϕ<110 deg., 140 deg.<=θ<=165 deg., 120 deg.<=ψ<=155 deg., and (3) 110 deg.<=ϕ<=120 deg., 120 deg.<=θ<=160 deg., 135 deg.<=ψ<=170 deg. are used.
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