Transition metal silicates, (ZrO2)(x)(SiO2)(1-x), have dielectric constants k > 10 that make them attractive for advanced Si devices. Band offset energies relative to Si are an important factor in determining tunneling leakage current, and internal photoemission. Studies by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and X-ray absorption spectroscopy (XAS) are combined with ab initio calculations to identify the compositional variation of the band-gap, and valence and conduction band offset energies of Zr silicate alloys with respect to Si. The minimum conduction band offset, due to Zr 4d* states, is shown to be independent of alloy composition, while valence band offsets decrease monotonically with increasing ZrO2 content. The implications of these results for direct tunneling are discussed. (C) 2003 Elsevier Science B.V. All rights reserved.