Method for manufacturing superconducting device having a reduced thickness of oxide superconducting layer and superconducting device manufactured thereby

Claim 2

A method claimed in Claim 1 wherein the c -axis orientated and a -axis orientated oxide superconductor thin films are formed of the same oxide superconductor material selected from the group consisting of a Y-Ba-Cu-O type compound oxide superconductor material, a Bi-Sr-Ca-Cu-O type compound oxide superconductor material, and a Tl-Ba-Ca-Cu-O type compound oxide superconductor material.

Claim 3

A method claimed in Claim 2 wherein the gate electrode is formed of a refractory metal or a silicide thereof.

Claim 4

A method claimed in Claim 2 wherein the gate electrode is formed of a material selected from the group consisting of Au, Ti, W, and a silicide thereof.

Claim 5

A method claimed in Claim 2 wherein the substrate is formed of a material selected from the group consisting of a MgO (100) substrate, a SrTiO₃ (100) substrate and a CdNdAlO₄ (001) substrate, and a semiconductor substrate.

Claim 6

A method claimed in Claim 2 wherein the substrate is formed of a silicon substrate having a principal surface coated with an insulating material layer which is formed of a MgAlO₄ layer and a BaTiO₃ layer.

Claim 7

A method claimed in Claim 2 wherein when the stacked structure including the gate insulator and the gate electrode is formed on the portion of the c -axis orientated oxide superconductor thin film, the c -axis orientated oxide superconductor thin film is selectively etched so that a portion of the c -axis orientated oxide superconductor thin film is completely removed and a surface of the substrate is exposed excluding a portion under the stacked structure, and a side surface of the remained c -axis orientated oxide superconductor thin film is coated with an normal conductor member, and wherein the a -axis orientated oxide superconductor thin film is grown on an exposed surface of the substrate.

Claim 8

A method claimed in Claim 7 wherein the gate insulator is formed of an insulating material which does not form a large density of energy levels between the oxide superconductor material of the c -axis orientated oxide superconductor thin film and the insulating material of the gate insulator.

Claim 9

A method claimed in Claim 7 wherein the c -axis orientated oxide superconductor thin film is formed to have a thickness of about 5 nanometers and the gate insulator is formed of MgO to have a thicknes of not less than 10 nanometers.

Claim 10

A method claimed in Claim 2 wherein after the gate electrode is formed, the c -axis orientated oxide superconductor thin film is selectively etched so that a portion under the gate electrode projects from the etched portion of the oxide superconductor thin film, the substrate is heated under high vacuum to make oxygen of the oxide superconductor crystals of the projecting portion escape and the oxide of the projecting portion becomes an oxide insulating layer, and a side surface of at least the gate electrode is covered with an gate insulating side-wall, the a -axis orientated oxide superconductor thin film is grown on an exposed surface of the c -axis orientated oxide superconductor thin film until the stacked structure is completely embedded in the a -axis orientated oxide superconductor thin film, and the a -axis orientated oxide superconductor thin film is planarized until an upper surface of the gate electrode is exposed at the planarized upper surface of the a -axis orientated oxide superconductor thin film.

Claim 11

A method claimed in Claim 10 wherein the gate insulator is formed of an oxide which is made of the same composition and has same crystal structure as those of the oxide superconductor constituting the c -axis orientated oxide superconductor thin film.

Claim 12

A method claimed in Claim 10 wherein the c -axis orientated oxide superconductor thin film is formed to have a thickness of about 20 nanometers and the gate insulator is formed to have a thickness of not less than 10 nanometers.

Claim 13

A superconducting device comprising a substrate having a principal surface, a first oxide superconducting region of an extremely thin thickness formed on the principal surface of the substrate, second and third oxide superconducting regions of a relatively thick thickness formed near each end of the first oxide superconducting region separated from each other, the first oxide superconducting region being electrically connected to the second and third oxide superconducting regions to bridge the second and third oxide superconducting regions and to form a superconducting channel between the second and third oxide superconducting regions, so that a superconducting current can flow through the superconducting channel between the second and third oxide superconducting regions, and a gate electrode formed on a gate insulator placed on the first oxide superconducting region for controlling the superconducting current flowing through the superconducting channel, the first oxide superconducting regions being formed of a c -axis orientated oxide superconductor thin film, the second and third oxide superconducting regions being formed of a -axis orientated oxide superconductor thin films, and the gate electrode being electrically isolated from the first, second and third oxide superconducting regions.

Claim 14

A superconducting device claimed in Claim 13 wherein the oxide superconductor thin film is formed of an oxide superconductor material selected from the group consisting of a Y-Ba-Cu-O type compound oxide superconductor material, a Bi-Sr-Ca-Cu-O type compound oxide superconductor material, and a Tl-Ba-Ca-Cu-O type compound oxide superconductor material.

Claim 15

A superconducting device claimed in Claim 14 the gate electrode is formed of a refractory metal or a silicide thereof.

Claim 16

A superconducting device claimed in Claim 14 wherein the gate electrode is formed of a material selected from the group consisting of Au, Ti, W, and a silicide thereof.

Claim 17

A superconducting device claimed in Claim 14 wherein the substrate is formed of a material selected from the group consisting of a MgO (100) substrate, a SrTiO₃ (100) substrate and a CdNdAlO₄ (001) substrate, and a semiconductor substrate.

Claim 18

A superconducting device claimed in Claim 14 wherein the substrate is formed of a silicon substrate having a principal surface coated with an insulating material layer which is formed of a MgAlO₄ layer and a BaTiO₃ layer.

Claim 19

A superconducting device claimed in Claim 14 wherein the gate insulator is formed of a material stable to the oxide superconductor material of the first, second and third oxide superconducting regions.

Claim 20

A superconducting device claimed in Claim 14 wherein the gate insulator is formed of an oxide which is made of the same composition and has same crystal structure as those of the oxide superconductor constituting the first oxide superconductor region.

Claim 21

A superconducting device claimed in Claim 14 wherein the first oxide superconducting region has a thickness of about 5 nanometers and the isolation region is formed of MgO or an oxide which is stable to the oxide superconductor material of the first, second and third oxide superconducting regions and has a thickness of not less than 10 nanometers.

Claim 22

A superconducting device claimed in Claim 14 wherein the gate insulating side-walls are provided on the both side surfaces of the gate electrode and formed of an insulator material, and the gate electrode is embedded in the oxide superconducting regions so that the gate electrode is isolated from the first, second and third oxide superconducting regions by the gate insulator and the gate insulating side-walls formed of the insulator material.