SUPERCONDUCTIVE ELEMENT

PURPOSE:To manufacture a superconductive element of stable characteristics with high yield, and operate it stably at the liquid helium temperature, by selecting the thickness of superconductor constituting a superconductive electrode so as to be thicker than three times the coherence length of the superconductor. CONSTITUTION:Boron is diffused with a density of 1X100 m in a Si substrate 41 whose face orientation is (100), on the surface of which a Nb thin film of 50nm thick is formed by electron beam deposition. This is subjected to reactive ion etching using CF4 gas to forma superconductive electrode 42. Then a SiO2 film of 100nm thick is formed by chemical vapor deposition, which is made into a gate-insulating film 43 by the similar reactive ion etching. Finally, an Al thin film of 150nm thick is formed by resistance heating deposition method, which is made into a control electrode 44 by means of lift-off method.