PURPOSE: To obtain a sensor which is simple for production as it can be produced in a production stage for ordinary semiconductor, has a long insulation life and is highly mechanical strength, by the constitution provided with a sensing part which reacts with a liquid to be inspected, a plane type semiconductor element having lead wires, and an insulator which exposes the sensing part of the semiconductor element and covers the entire part.

CONSTITUTION: A base 14 is put into a lower mold 17, and a plane type semiconductor element 6 is placed in the recessed part of the base 14; further a silicone rubber piece 15 as a polymer elastic material is put on the sensing part. Lead wires 13 are adequately disposed, and an upper mold 16 is stacked on the mold 17 and both molds are fixed by means of a metallic clamp, etc. An epoxy resin compsn. is vacuum-defoamed and is put into an injector having a needle- like injection part, by which the compsn. is injected into the molds through the injection hole 18 of the mold 16. The molds are put into an electric oven kept at a prescribed temp. upon thorough injection of the epoxy resin compsn., and the resin is cured for a required temp. The upper and lower molds are removed after curing and the plane type semiconductor element coated with the expoxy compsn. is removed.