Transition metal silicates, (ZrO2)(x)(SiO2)(1-x), with dielectric constants, k > 10 have been proposed as alternative dielectrics for advanced Si devices. Studies by X-ray absorption, X-ray photoelectron and Auger electron spectroscopy are combined to identify the compositional variation of the valence and conduction band offset energies with respect to Si in Zr silicate alloys. The minimum conduction band offset energy, associated with localized Zr 4d*-states, is similar to1.4 eV, and is independent of alloy composition, while valence band offsets decrease monotonically with increasing ZrO2 content. Differences between the coupling of tunneling electrons to localized Zr 4d* and extended Si 3s* states, characterized by respective tunneling masses of similar to0.5m(o) and similar to0.2m(o), combine to contribute to a minimum in the direct tunneling current in the mid-silicate-alloy composition range. x similar to 0.4-0.6. (C) 2003 Elsevier Science B.V. All rights reserved.