  We report the electrical transport in vertical Josephson tunnel junctions
(area 400 $\mu m$$^2$) using GdBa$_2$Cu$_3$O$_7$$_{-\delta}$ electrodes and
SrTiO$_3$ as an insulating barrier (with thicknesses between 1 nm and 4 nm).
The results show Josephson coupling for junctions with SrTiO$_3$ barriers of 1
nm and 2 nm. The latter displays a Josephson of 8.9 mV at 12 K. This value is
larger than the usually observed in planar arrays of junctions. Our results are
promising for the development of superconducting electronic devices in the
terahertz regime.

Superconductivity