PURPOSE: To enable a thickness to be controlled accurately with a small number of processes by making a single-crystal silicon of a first substrate corresponding to a recessed portion a flexible elastic body which is born by a second substrate and the deflection to be detected by a strain gauge.

CONSTITUTION: A first substrate 1 consisting of a thin single-crystal silicon and a second substrate 2 consisting of a silicon which is joined to this first substrate 1 through an insulation film 3 are provided. A recessed portion 4 which is dug by etching until at least the insulation film 3 is reached by a specified pattern from a rear surface side of the second substrate 2 and a strain gauge 6 which is created by diffusion at a surface portion of the first substrate 1 corresponding to this recessed portion 4 are provided. With a single-crystal silicon of the first substrate 1 corresponding to the recessed portion 4 as a flexible elastic body which is born by the second substrate 2. the deflection is detected by the storage gauge, thus enabling a thickness of the elastic body when performing mass-production of a semiconductor sensor to be controlled easily and accurately.