SUPERCONDUCTING SWITCH ELEMENT

PURPOSE:To enable switching operation even in DC bias currents by bringing the size of one side of a barrier layer section, through which tunnel currents can flow, to a specific value or less, constituting all or one part of said barrier layer by Si or a Si oxide and forming all or one part of them on a plane, which does not contain the film end section or bend section of a lower electrode. CONSTITUTION:The barrier layer 17 is formed in such a manner that a Nb lower electrode film 15 is formed and an Si film is formed on the film 15 through a high-frequency sputtering method in the thickness of 2mum without breaking vacuum and oxygen is introduced into a vacuum device before evaporating an upper electrode 18 and the Si film is thermally oxidized. Junctions of 1.5X1.5mum, 2X2mum and 1.5X1.5mum are arranged in parallel in junction sections to constitute a quantum interferometer. When the Si oxide is used as the barrier layer 17, zero voltage return currents Imin reach 30% or more to a critical current value when a junction area is 2X2mum or less, and a voltage value corresponding to a Imin value reaches 80% or more of gap voltage. The region corresponds to a region, which can be operated practically by a bias by a DC power supply.