Abstract: When green sheets are laminated and integrally fired for a window spacer plate formed with at least a plurality of windows, a covering plate for covering the windows, and a through hole plate having through holes, communicating with the windows, it is arranged to make a ratio t/w of thickness t of the green sheet for the window spacer place to length w of the through holes formed in the green sheet for the through hole plate, in its minor axis direction one or more, and to form a functional film actuator on the outer surface of the covering plate after firing. A gap (separation) is prevented from being generated in the interface between each ceramics plate in producing a ceramics substrate used for the functional film element.