In order to get insight into the origin of deterioration of epitaxial layers on Si substrates, crystallographic aspects of CeO2(110) layers grown on Si(100) substrates are studied using atomic force microscopy, X-ray diffraction and cross-sectional transmission electron microscopy in correlation with crystalline quality of the layer determined by reflection high-energy electron diffraction. It is found that surface morphology changes with crystallinity of the CeO2 layers. Single crystalline CeO2(110) layers with excellent crystallinity have a nanometer-scale-periodically corrugated surface structure, which consists of (111)-facets. As the crystalline quality of the CeO2 layers becomes worse, the number of irregular shaped hillocks increases, which correspond to distorted (110)-grains. It is found that crystalline quality is not uniform but different crystallinity regions are distributed from place to place and their population ratio changes according to the degree of crystalline quality. Direct observation of the irregular shaped hillocks is carried out from cross-sectional lattice images of high-resolution transmission electron microscopy. It is found that the irregular shaped hillock is inclined by similar to5degrees. (C) 2003 Elsevier Science B.V. All rights reserved.