Method of producing ceramic diaphragm structure having convex diaphragm portion

A method of producing a ceramic diaphragm structure including a ceramic substrate having at least one window, and a ceramic diaphragm plate which is superposed on said ceramic substrate so as to close said at least one window, comprising the steps of:

• firing said diaphragm plate with said ceramic substrate to form an integral sintered body, such that said diaphragm plate provides at least one diaphragm portion which is respectively aligned with said at least one window;
• protruding each of said at least one diaphragm portion outwards, in a direction away from a corresponding one of said at least one window, so that said each diaphragm portion is formed into a convex shape;
• and
• controlling an amount of protrusion of said at least one diaphragm portion, by pressing a jig having a flat surface or a concave surface, against a top part of said each diaphragm portion having the convex shape, so that at least said top part has a flat surface or a curved surface having a predetermined radius of curvature.