Wide-gap insulator films, CaZrO3, CaHfO3, LaGaO3, and NdGaO3, were grown on SrTiO3(1 0 0) substrates with the aim of obtaining a gate insulator for epitaxial oxide devices. We show that CaZrO3 and CaHfO3 films were epitaxial and had a multi-domain in-plane structure due to their highly distorted perovskite structure. Most of the LaGaO3 and NdGaO3 films were polycrystalline, and therefore showed relatively high leak currents. CaHfO3 had the best crystallinity among these four materials. (C) 2003 Elsevier Ltd. All rights reserved.