A method of manufacturing a surface acoustic wave device

A method of manufacturing a surface acoustic wave device including a substrate, a surface of which has at least one piezoelectric function, and an electrode formed on the substrate, comprising the steps of: Forming a first film of Al containing Cu at or above the solid solubility limit of Cu compared to Al, on the substrate; includes forming one or more unit (s) of a second film of Al, Mg at or above the solid solubility limit of Mg compared with Al, and a third film made of Al containing Cu at or above the solid solubility limit of Cu compared to Al, in this order on the first film; and thermally treating the first, second and third films at a temperature of 100 to 350 ° C to diffuse Mg in the second film in the first and third films, whereby the electrode is formed.