SURFACE ACOUSTIC WAVE DEVICE AND METHOD OF PRODUCING THE SAME

摘要

A surface acoustic wave filter element is constructed in a manner such that a conductive film, which constitutes a plurality of electrode fingers, a bus bar connecting the electrode fingers in common, an electrode pad connected to the bus bar, etc., is formed on a piezoelectric substrate. When using the surface acoustic wave filter element with this arrangement in a high-frequency band, the thickness of the conductive film and the line width of electrodes are reduced, so that the mechanical strength is a critical problem. According to the present invention, therefore, the conductive film has a two-layer structure, including a layer containing tantalum and aluminum and a metallic layer of aluminum or an alloy consisting mainly of aluminum formed thereon, for example. The composition ratio between tantalum and aluminum is set so that the tantalum content ranges from 39% to 75% (atomic percentage). Thus, the orientation the layer of aluminum or the alloy consisting mainly of aluminum, formed on the layer containing tantalum and aluminum, is improved to increase the strength of the conductive film.