This work investigates the bulk properties, the surface morphology, and the electrical interfacial characteristics of the Ta2O5-based high-k dielectric (epsilon r similar to 20) produced by Ta2Si deposition and subsequent oxidation directly on 4H-SiC substrates in the oxidation temperature range 750-1050 degrees C. Electron microscopy measurements show that this insulator layer consists of a combination of delta-Ta2O5 grains and amorphous SiO2 intergrain channels. An interfacial SiO2 based layer is also evidenced. The surface roughness of the insulator diminishes when oxidation temperature increases. Annealing in N-2 the dielectric layers improves the interface characteristics for samples oxidized at 850 and 950 degrees C where 4H-SiC substrate oxidation is negligible. (C) 2004 The Electrochemical Society.