| 摘要 |
PROBLEM TO BE SOLVED: To set frequency temperature characteristic to be optimal within a desired temperature range and to remarkably improve yield of a surface acoustic wave device by properly setting film thickness of a silicone dioxide film. SOLUTION: An IDT electrode 3 is arranged along the propagating direction of the surface acoustic wave to be excited by a 45 deg. X cut lithium tetraborate substrate 1 and reflectors 4a, 4b are arranged on both sides of the electrode 3. The IDT electrode 3 is constituted by a pair of comb-line electrodes with plural electrode fingers to be inserted into each other, one comb-like electrode of the IDT electrode 3 is connected to an input terminal IN and the other comb-line electrode is connected to an output terminal OUT. Then only a desired surface acoustic wave among plural surface acoustic waves excited by the IDT electrode 3 is locked between the reflectors 4a, 4b and is actuated as a SAW resonator. Ratio Hs/λbetween the film thickness Hs of the silicon dioxide film 2 and the wavelengthλof the surface acoustic wave to be excited in within the range of 5×10<-4> <=HS/λ<=5×10<-3> .
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