Abstract: A semiconductor device in which intrusion of the cutting water and cutting wastes in the singulation process can be prevented, and reliability is improved includes: a substrate; at least one semiconductor element having a piezoelectric conversion function and mounted on the main surface of the substrate; a casing fixed to the main surface of the substrate to cover the semiconductor element; a through hole formed in the substrate or the casing; and a predetermined substance filled into the through hole to close the through hole, wherein the predetermined substance has properties such that the predetermined substance wettably spreads by heating to open the through hole.