The current status of epitaxial technology towards high Tc electronics is summarized. Properties and processing maturity were compared for various oxide single crystals to give hints for the choice of substrate. Such problems in YBa2Cu3O7 (YBCO) film growth as precipitate formation and cracking were quantitatively investigated and shown to be solved by carefully preparing the substrate surface and by optimizing buffer layers and growth conditions. It is now possible to perform ideal layer-by-layer growth of various oxide films on atomically flat substrates by laser MBE to explore not only high Tc electronics but also a possible new field of oxide electronics.
An overview of present Josephson junctions based on high-temperature superconductors (HTSs) is described. I indicate the importance of the critical current-normal resistance (IcRn) product, and show the experimentally-obtained values of the IcRn products for the HTS Josephson junctions reported so far. The junctions include grain boundary junctions, edge junctions, and sandwich junctions. Considering the charge transport mechanism across the junctions, effective ways to increase the IcRn product are proposed.