PURPOSE: To obtain an FET type semiconductor sensor which is operable with a high sensitivity and even on a high power source voltage.

CONSTITUTION: It is assumed that the quantity of impurities per unit area of a P type low impurity density silicon substrate layer 2 is set at Pscm-2 while the quantity of impurities per unit area of an N type low impurity density surface layer 5 at Q1cm-2. If the quantity of impurities in the sensor area is selected so that Q1 is slightly less than Qs, the relationship of the impurities quantity in the sensor area shifts to Q1+ΔQ1>Qs from Q1<Qs when Q1 increases equivalently to Q1+ΔQ1 due to a charge generated in a response film. At this point, the potential of a measuring terminal changes to the voltage of an electrode 9 from a depletion layer voltage of the N type low impurity density surface layer 5. The potential of the measuring terminal shifts to 100V from about 20V to produce a large voltage change. This enables the manufacture of a pressure sensor using as a sensitive film a film adapted to generate potential by pressure.