Method of producing a josephson tunnel barrier

Abstract

A method for producing multi-layered Josephson tunnel barrier devices without an edge step between the layers comprises the steps of forming a first layer containing at least a lower layer superconducting film on a substrate, selectively removing the surface portion of the first layer, except an area where a Josephson tunnel barrier is to be formed, to a predetermined first depth, and forming a first insulating film, preferably by a high-directivity film forming method, on the removed portion of the first layer in such a thickness that the insulating film surface is substantially coplanar with the surface of the retained area of the first layer. A tunnel barrier may be subsequently formed after the third step or in advance following formation of the first layer in the first step, thereby eliminating a change in the characteristics of the tunnel barrier due to the atmosphere. Prevention of edge step is enhanced by forming a lower layer superconducting film on the substrate, patterning the lower layer superconducting film to form a first superconducting electrode, forming a first insulating film having a predetermined thickness over the entire area of the substrate, and selectively removing a surface portion of the first superconducting electrode except a predetermined portion thereof and a surface portion of the first insulating film such that any edge step between the boundary of the first superconducting electrode and the first insulating film is eliminated.