Superconducting device and a method for manufacturing the same

A superconducting device comprising:

• a substrate having a diffusable element therein, said diffusable element being diffusable from said substrate,
• a pair of superconducting electrode regions formed by a thin film of oxide superconductor having a sufficiently thick wall-thickness on said substrate,
• a weak link region, and
• a gate insulating layer on said weak link region,
• said superconducting electrode regions being positioned at opposite sides of said weak link region,
• said superconducting electrode regions and said weak link region being formed on a common plane surface of said substrate, and
• said weak link region comprising a diffusion region and a superconducting region, said diffusion region being non-superconducting and including a portion of said element from said substrate and a first portion of said thin film of oxide superconductor which contains said portion of said diffusable element therein, said superconducting region including a second portion of said thin film of oxide superconductor which corresponds to said weak link region, said second portion having a thickness from said diffusion region to an upper surface of said thin film for forming a superconducting channel in said thin film of oxide superconductor over said non-superconducting diffusion region,
• said diffusion region being formed by heating said thin film of oxide superconductor, at said weak link region, whereby, among said gate insulating layer, said thin film of oxide superconductor, and said substrate, the highest temperature thereamong is not less than 600.degree. C. and not more than 700.degree. C.,
• said diffusion region thereby having a profile including, in a direction substantially perpendicular to said substrate, a curved uppermost section located beneath said superconducting region and opposing curved side sections that each curve outwardly and downwardly away from said uppermost section toward said substrate.