Preparation of high quality single crystal Nb tunnel junctions based on Nb/Nb2O5/Pb structures is reported.Vmvalues of 30±10 mV were obtained. The average specific capacitance of these junctions is 0.020±0.002 pF/&mgr;m2. From measurements of the oxidation rate, the conductance at high voltage bias, and observations of the tunneling behavior, we show that some characteristics previously associated with oxidized niobium barriers are not intrinsic and are significantly improved when the underlying niobium film is single crystal.