We present a fabrication scheme and testing results for epitaxial
sub-micrometer Josephson junctions. The junctions are made using a
high-temperature (1170 K) "via process" yielding junctions as small as 0.8 mu m
in diameter by use of optical lithography. Sapphire (Al2O3) tunnel-barriers are
grown on an epitaxial Re/Ti multilayer base-electrode. We have fabricated
devices with both Re and Al top electrodes. While room-temperature (295 K)
resistance versus area data are favorable for both types of top electrodes, the
low-temperature (50 mK) data show that junctions with the Al top electrode have
a much higher subgap resistance. The microwave loss properties of the junctions
have been measured by use of superconducting Josephson junction qubits. The
results show that high subgap resistance correlates to improved qubit
performance
