Method for making a superconducting field-effect device with grain

Abstract

Disclosed is a method for making a superconducting field-effect device with a grain boundary channel, the method comprising the steps of depositing a first superconducting thin film on a substrate; patterning the first superconducting thin film to form a patterned superconducting thin film having an opening; depositing a template layer thereon; selectively etching back the template layer to form a patterned template layer; growing a second superconducting thin film to form a grain boundary therebetween; depositing an insulating layer on the second superconducting thin film to protect the second superconducting thin film from degrading in property in the air; selectively etching back the insulating layer to form a patterned insulating layer; forming a gate insulating layer on the patterned insulating layer; and coating metal electrodes thereon, source/drain being formed respectively on the etched portions, and a gate electrode being formed on the deposited portion of the gate insulating layer directly above the grain boundary. In the superconducting FET manufactured thus, since a gate electrode is formed directly above a grain boundary, current flowing between source and drain can be controlled by a voltage applied through an gate insulating layer. Also, since the grain boundary serving as a channel can be formed in a cheaper oxide crystal substrate by variation in a growing temperature of thin film without using an expensive by-crystal substrate, a high-temperature superconducting FET can be economically fabricated.