The microstructure of thin HfO2-Al2O3 nanolaminate high kappa dielectric stacks grown by atomic vapor deposition has been studied by attenuated total reflection spectroscopy (ATR) and 8 eV spectroscopic ellipsometry (SE). The presence of Al2O3 below HfO2 prevents the crystallisation of HfO2 if an appropriate thickness is used, which depends on the HfO2 thickness. A thicker Al2O3 is required for thicker HfO2 layers. If crystallisation does occur, we show that the HfO2 signature in both ATR and 8 eV SE spectra allows the detection of monoclinic crystallites embedded in an amorphous phase. (c) 2010 Elsevier B.V. All rights reserved.