The microstructure ofYBa2Cu3O7−&dgr;(YBCO) grain boundaries obtained at step edges on (001)LaAlO3substrates have been studied by scanning and transmission electron microscopy. A typical morphology of the YBCO grain boundaries is distinguished by two parts where the parts are expected to have different junction properties. One part of the boundary is caused by the difference in nucleation probability between the (001) surface and the inclined step facet. The second morphology is developing as a result of minimization of the YBCO surface energy. ©1997 American Institute of Physics.