JPS57148242A - Electrostatic capacity sensor - Google Patents

Abstract

PURPOSE:To enable increasing of an electrostatic capacity, by a method wherein an opposed electrode, consisting of a reverse conductive layer made of a similar material to that of a semiconductor substrate, is placed on the semiconductor substrate as a measuring sensor for, for example, alcohol concentration, and the opposed electrode is separated with a recess extending all the way through to the substrate. CONSTITUTION:Opposed electrodes 11 and 12 are formed on a plane substrate 13 made of a p type silicon such that diffused n type reverse conductive layers 11 and 12 are cut in a V-recess so that the recess extends all the way through to the substrate 13. Simultaneously, an oxidized film 14 is formed on the electrodes 11 and 12. A V-recess 17, separating the electrodes 11 and 12 in a manner described above, is formed in a direction 110, and a recess wall forms a surface 111 to form an approximately accurate V-shape at a cutting angle of 54.7 deg. to the surfaces of the electrodes 11 and 12. An oxidized film 15 is then formed on the surface of the V-recess 17 to cover an end surface of a P-N junction. An aluminum, electrode 16 is further formed on the electrodes 11 and 12 to obtain an electrostatic capacity sensor. A diffusion depth is brought to nearly similar depth to that of the recess 17 in a manner described above, and this permits the sharp increase in an electrostatic capacity.