A semiconductor strain sensor having a stem with a lead hole in which a lead terminal is installed and electrically coupled to an external circuit. A sensor chip having piezo-resistors to a bride circuit is joined with a front surface of the stem. A shell is joined with the front surface of the stem by projection welding after the back surface of the stem is flattened to within a predetermined limit. A space formed by the shell and stem is filled with a damping liquid. The stem is integrally coupled to the sensor chip through an adhesive, and spacers are added to the adhesive to keep the thickness of the adhesive to a predetermined value. This arrangement can effectively prevent propagation of the welding strain of the stem from adversely affecting the sensor chip.