A chip substrate includes conductive portions, an insulation portion and a cavity. The conductive portions are laminated in one direction to constitute the chip substrate. The insulation portion is interposed between the conductive portions to electrically isolate the conductive portions. The cavity is formed on an upper surface of the chip substrate at a predetermined depth in a region including the insulation portion. The cavity is defined by a plurality of continuously-extending curved surfaces having predetermined radii of curvature.