A surface wave filter element includes a portion on which elastic surface waves propagate. This portion includes a piezoelectric material, an amorphous boron layer or plate and IDT electrodes for inputting and outputting signals. The piezoelectric material is a film made of ZnO, LiNbO3 or LiTaO3 formed by sputtering, ion beam deposition or chemical vapor deposition. The amorphous boron layer or boron plate may be formed on a substrate made of an inorganic material. The boron material is formed using electron beam deposition, ion beam deposition or chemical vapor deposition.
