Formation of Frank-type faults on the basal plane in 4H-SiC{0 0 0 1} epitaxial growth has been investigated by grazing incidence synchrotron reflection X-ray topography and transmission electron microscopy. The Frank faults, which are formed by conversion of a 1c threading screw dislocation (TSD) in the substrate as well as simultaneous generation of a le TSD during epitaxial growth, are confirmed to be created by four Frank partials with a Burgers vector of 1/4[0 0 0 1] type having the same sign on four different basal planes. The fine features of the X-ray topography contrast are confirmed to reflect the microscopic structure of the Frank faults. A variety of Frank fault formation has been revealed by comparing topography images taken before and after epitaxial growth. The formation mechanism of the Frank faults is discussed based on the evaluated microscopic structures. (C) 2007 Elsevier B.V. All rights reserved.