This paper describes the fabrication and evaluation of dielectric‐base transistors having high‐TcYBa2Cu3O7−xelectrodes with NdGaO3low‐permittivity barriers on SrTiO3high‐permittivity substrates. The YBa2Cu3O7−x/NdGaO3/SrTiO3heterostructures were made by laser ablation. Nb base electrodes were sputtered on the back of the SrTiO3substrate. The device showed transistor characteristics with voltage and current gains exceeding unity at 4.2 K. The collector current density was about 10 A/cm2at a collector voltage of 20 V, four orders of magnitude larger than that obtained for devices having no artificial barriers.