CERAMIC SUBSTRATE AND MANUFACTURING METHOD THEREFOR

A ceramic substrate (10) having a cavity which can be used for measuring the thickness of the substrate includes a plurality of stacked ceramic substrate members (1). Each of the plurality of ceramic substrate members (1) includes a via (2) reaching the other main surface from one main surface. A gap (6) is formed in each of first and second ceramic substrate members (1a, 1f) of the plurality of stacked ceramic substrate members (1) to penetrate each of the first and second ceramic substrate members (1a, 1f), the first ceramic substrate member (1a) being arranged at an outermost surface on one side in a stacking direction of the ceramic substrate members (1), the second ceramic substrate member (If) being arranged at an outermost surface on the other side opposite to the one side in the stacking direction. At least a portion of a side surface and a bottom surface within the gap (6) are covered with a protection layer (7, 8). The protection layer (7, 8) is made of a material having an etching rate lower than that of the ceramic substrate members (1).