Abstract: A superconducting device has an oxide superconducting material with a passivation or blocking film formed on its surface. The film helps to maintain a uniform oxygen concentration of the superconducting material through its thickness. The superconducting material is thus superconductive throughout its cross-section, and particularly in the vicinity of the surface bearing the film.

Abstract: An oxide-superconducting device comprises first and second electrodes of oxide-superconductor which are connected through a tunnel barrier layer. The oxide-superconductor is formed on a substrate having a recess, and it includes grain boundaries along the recess. The tunnel barrier layer is formed along the grain boundaries, and it is made of any material of an element F, Cl, Br, I, C, O, S, P or N, a mixture consisting of such elements, and a compound containing such an element, the material being introduced into the grain boundaries and/or lattice interstices near the grain boundaries.