a bicrystal substrate is formed by joining end faces of a first single crystal substrate and a second single crystal substrate , the end faces having different crystal orientations . a high critical temperature superconducting thin film is then epitaxially formed on the bicrystal substrate . the superconducting thin film is etched so as to form a first superconducting electrode on the first single crystal substrate , a second superconducting electrode on the second single crystal substrate , and a superconducting bridge across a joint between the first and second single crystal substrates and connecting the first electrode and the second electrode . a conductive film is formed on the superconducting bridge by vapor deposition , and is then etched so as to form a weak link on a part of the superconducting bridge over the joint .