Abstract: The present invention relates to a gas sensor and a gas discriminating method which are capable of distinctly discriminating two or more kinds of gases. A DC bias and AC signals which are superposed to a junction part, which is formed on a gas sensor having a p-type oxide semiconductor and an n-type oxide semiconductor by means of heterojunction of end surfaces thereof, an impedance characteristic of the junction part is measured, and CO gas and H.sub.2 gas are discriminated in accordance with a dependence on a frequency of the AC signals and on the DC bias of the impedance characteristic. CuO into which an alkali metal element is doped is used as the p-type oxide semiconductor and ZnO is used as the n-type oxide semiconductor. The alkali metal element to be used is an alkali metal element selected from the group of Li, Na and K and the doping quantity is such that 0.2 mole %.ltoreq.M.sub.2 O.ltoreq.5 mole %, where M is Li, Na or K.

Abstract: A semiconductor device, by which a base in which gates are buried can be formed by the junction of semiconductor substrates to each other at a lower temperature, and a fabrication process thereof are provided. Recesses are defined in the top of an N.sup.- substrate. A P.sup.+ layer is formed on the underside of the N.sup.- substrate. P.sup.+ -Gate regions are each formed in an area ranging from the bottom to lower side portions of the recesses. A metal layer composed of an Au-Sb alloy is formed on the underside of the N.sup.+ substrate. The N.sup.- substrate and the N.sup.+ substrate are subjected to a treatment for removing impurities thereon with an aqueous solution of sulfuric acid and hydrogen peroxide, washed with purified water and dried by a spin dryer. The N.sup.- substrate and the N.sup.+ substrate are heated at about 350.degree. C.

Abstract: A coating comprising chromium and nitrogen is formed on the sliding substrate surface of a sliding component. The chromium concentration of the coating is continuously and gradually increased from the substrate surface in a perpendicular direction toward the surface of the coating.A coating having good wear resistance and initial conformability is obtained.