Abstract: The present invention provides a process for producing a superconducting transistor on a surface of an insulating substrate. A pre-superconducting thin film contains a material that can be changed into a superconductor during subsequent processing but which is initially a non-superconductor. A thin film containing the material required by the pre-superconducting thin film is deposited in a preferred pattern on the pre-superconducting thin film. The assembly thus formed is heat treated to permit the material from the thin film to enter the pre-superconducting thin film, thereby forming superconducting regions in the pre-superconducting thin film in the preferred pattern. The superconducting regions form electrodes of the transistor.