Interface formation between high-k dielectric oxide materials and semiconductor surfaces is of critical importance to the development of the next generation of high speed semiconductor devices. This thesis investigates the deposition and characterisation of a range of candidate high-k materials on both silicon and III-V (InGaAs and InP) semiconductor substrates, with the focus on interface formation.The primary characterisation techniques used to study the interface chemistry were x-ray photoelectron spectroscopy (XPS) and synchrotron radiation based photoemission, while atomic force microscopy (AFM) was used in some experiments for surface roughness measurements. The first part of the study evaluates a range of surface preparation methods prior to dielectric deposition aimed at removing the native oxides and passivating the surfaces while keeping surface roughness to a minimum. Methods investigated for silicon surface preparation included flash cleaning, hydrofluoric acid (HF) etching and the growth of self limiting ultra-thin oxides. For InGaAs the optimisation of the ammonium sulphide (NH4)2S and hydrogen sulphide (H2S) passivation treatments was investigated and an in-depth study of atomic hydrogen cleaning was undertaken. For InP surfaces, an (NH4)2S based treatment was compared to an alternative acid based etch. The dielectric/substrate systems investigated included the reactive deposition of magnesium oxide (MgO) on Si studied by XPS and synchrotron radiation photoemission and aluminium oxide (Al2O3) deposited by atomic layer deposition (ALD) on indium gallium arsenide (InGaAs) also studied by XPS. Electron beam deposition studies of HfO2 were also carried out on InP after various surface treatments, followed by XPS and electrical characterisation to determine the effect of the surface treatments in terms of native oxide and defect generation.