| 摘要 |
PROBLEM TO BE SOLVED: To use a relatively inexpensive wet etching process to realize an inexpensive filter by forming an anodic oxidation film having a specific film thickness on the surface of an electrode film constituting a surface acoustic wave resonator. SOLUTION: This filter consists of a surface acoustic wave resonator 5, a 36±3 deg.X-Y LiTa03 substrate 6, IDT electrodes 7 and 8 exciting a surface acoustic wave, and reflectors 9 arranged on both sides of IDT electrodes 7 and 8. Electrode fingers are arranged at prescribed intervals. Aluminium or aluminium alloy including Cu is stuck to a piezoelectric substrate by vapor- deposition, sputtering, or the like and is etched to form the IDT electrodes 7 and 8 and reflectors 9. In this case, IDT electrodes 7 and 8 and reflector electrodes on the 36 deg. Y cut-X LiTaO3 substrate 6 are formed with film thickness which is about 4 to 6% of the wavelength and is not extremely thick, and the mass of electrodes is increased by the anodic oxidation technique, thus obtaining the same effect as thicker film thickness.
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