PURPOSE: To prevent the generation of the transmission defective due to the disconnection caused by the soldered corrosion of the root electrode of a leading electrode by forming a protective film for soldered corrosion prevention at the root of the leading electrode led from the IDT electrode formed on an SAW substrate.

CONSTITUTION: On the SAW piezoelectric substrate 2 of an SAW chip 1, two input/output IDT electrodes 3 are formed adjacently. A reflector electrode 4 on the external side of the electrode 3 and the leading electrode 5 derived from the electrode 3 are formed of metal A 1 by deposition, sputtering, etc. At the root of the electrode 5, protective films 5a such as SiO2, SiNx, etc., are formed on the electrode A1. On the part of the protective films 5a and the leading electrode 5, an Ni layer 6a and an Ag layer 6b are successively formed. The protective films 5a prevent the disconnection due to soldered corrosion, and the Ni layer 6a and the Ag layer 6b improves the soldered connection. The SAW chip 1 is placed by inverting the chip on the chip carrier where a metallized wiring electrode is formed, the electrode 5 and the metallized wiring electrode are connected by soldering, the chip carrier is covered with a cap and they are joined and sealed.