Insituplanarization of epitaxial films has been demonstrated. This is a critical technology for the processing of any epitaxial multilayer device. Ion beam assisted deposition (IBAD) has been used to planarize patterned yttria‐stabilized ZrO2(YSZ)(001) substrates using YSZ films. X‐ray diffraction measurements have shown that the IBAD YSZ grows homoepitaxially. The IBAD planarization mechanism has similarities to those previously observed for rf bias sputtering. Critical current densities of up to 7×105A/cm2at 77 K have been measured for Ba2YCu3O7−x(BYC) films deposited on planarized patterned YSZ substrates using pulsed laser deposition. In contrast, BYC deposited on unplanarized patterned YSZ substrates did not become fully superconducting for measurements down to 25 K. ©1995 American Institute of Physics.