PURPOSE: To be able to sufficiently utilize a superconducting carrier for oozing two-dimensional carrier gas layer from an ohmic electrode of a superconductor thereby to produce a large superconducting current by using an HEMT as a transistor which becomes a base.

CONSTITUTION: A nondoped InAs active layer 4 made of an Incontaining compound semiconductor for generating two-dimensional carrier gas, a carrier supply layer (e.g., n+-type InxGa1-xAs electron supply layer) 6 made similarly of the In-containing compound semiconductor, ohmic electrodes (e.g., a source electrode 9 and a drain electrode 10) made of a pair of superconductors for supplying a superconductive current through the two-dimensional carrier gas formed near the active layer, and a gate electrode 11 formed between the pair of ohmic electrodes for controlling carrier concentration in the two-dimensional carrier gas layer are sequentially formed on an InP substrate 1. Thus, the superconducting carrier oozed from the ohmic electrodes of the superconductor to the two-dimensional carrier gas layer can be sufficiently utilized to produce a large superconducting current. The mobility of the carrier is very high.