Abstract: A reference electrode of an insulated gate field effect transistor having the surface of the gate region thereof coated with a hydrophobic organic polymer membrane. Since this reference electrode is much smaller in size than conventional reference electrodes, an integrated measurement system can easily be constructed by using this reference electrode. This measurement system is especially effective for measuring various ions in the living body.

Abstract: A selective chemical sensitive field-effect transistor device for use in detection and measurement of chemical properties of substances to which the device is exposed is disclosed. The chemical sensitive FET device comprises a semiconductor substrate, at least one pair of spaced apart diffusion layers formed on one surface of the semiconductor substrate and forming source and drain regions, respectively, and a double layer structure consisting of a silicon oxide layer and an electrically insulating layer overlaying the silicon oxide layer. A gate region located on a portion of the surface of the semiconductor substrate between the diffusion layers is overlaid with a chemical selective membrane adapted to interact with certain substances. A method for the manufacture of the above described FET device is also disclosed.