<p>By sealing a diaphragm (150) with less processes and lower cost and reducing deformation due to remaining stress, a stable and highly reliable pressure sensor construction is proposed. The pressure sensor is low in measurement error and small in floating capacitance and leakage current and good in characteristic. As a means to attain the above object, a polycrystalline silicon diaphragm (150) is sealed with a silicon oxide film (160) deposited through a LPCVD method and then completely covered. The diaphragm (150) is placed on a surface of a semiconductor substrate (110) with a nearly constant gap of 0.15 to 1.3 mu m, and has difference-in-grade constructions (40) of a deformation reducing means due to remaining stress. <IMAGE></p>
