A surface acoustic wave filter element and a method of producing the same.
The 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.