A method of forming a lithium coating on a substrate, the method comprising: melting a solid lithium target to form a molten lithium target; agitating the molten lithium target; vaporising at least part of the agitated molten lithium target to form a vaporised material; and condensing the vaporised material on a substrate to form a lithium coating.

A method for manufacturing an acoustic wave device with an excellent frequency-temperature profile is performed such that the acoustic wave device produced includes a piezoelectric substrate, an IDT electrode located on the piezoelectric substrate, and a dielectric film mainly including Si and O and arranged on the piezoelectric substrate to cover the IDT electrode. The dielectric film is formed by sputtering in a sputtering gas containing H.sub.2O.