High aspect ratio trenches were patterned on (100) LaAlO3 substrates by focused ion-beam milling prior to film deposition. Subsequent YBCO films deposited by pulsed laser deposition were found to break naturally across these trenches. In situ Au was then deposited to connect the separated YBCO electrodes. Junctions were then patterned across the trenches to form a superconductor/normal/superconductor configuration. The resistively shunted junctions exhibited supercurrents up to 86 K. Under microwave irradiation, the junctions exhibited a number of clear Shapiro steps in the I–V characteristics. The transverse magnetic-field diffraction pattern indicted uniform current distribution across the junction. © 1998 American Institute of Physics.