SURFACE ACOUSTIC WAVE FILTER

摘要

In a surface acoustic wave (SAW) filter having a substrate and electrodes formed on the substrate, an electrode has a base layer, a first metal layer made of Al or an Al-based metal and oriented in a constant direction to the substrate, a second metal layer which prevents Al atoms of the first metal layer from migrating vertically to the substrate, and a third metal layer for adjusting the film thickness. Thus, a SAW filter having an arbitrary film thickness enables the simultaneous attainment of a film quality of difficulty in grain boundary diffusion and micronization of the grain diameter of a film effective in stress resistance. Therefore, the SAW filter blocks the migration of Al atoms of the electrode due to a stress loaded on the electrode with the propagation of the SAW, so that the filter becomes excellent in power resistance.