Submicron YBa2Cu3O7−xbicrystal grain boundary junctions have been fabricated, for the first time, by a focused ionbeam process. Although such a process has always been considered detrimental to theYBa2Cu3O7−xbecause of gallium contamination, high quality24° [001] tilt junctions characterized by RSJ current–voltage characteristics,ICRN products ofthe order of 1–4 × 104 A cm−2 at 77 K and Fraunhofer-like modulation patterns have been obtained. No significantdegradation has been observed over more than 3 months.The critical current density JC and the characteristic voltage ICRN show a clear maximum for widths of the order of the Josephsonpenetration depth. The asymptotic normal resistance shows a typical(width)−1 dependence, indicating that the FIB process does not increase the grain boundaryresistivity of submicron junctions.Experimental results clearly show that FIB is a very powerful tool for the fabrication ofhigh critical temperature superconducting circuits, requiring a small number of submicronJosephson junctions, and for fundamental physics analysis. It also allow the final tuning orrepair of superconducting or more complex integrated superconducting–semiconductingdevices.