In this work, various insulator/semiconductor interfaces on silicon, gallium arsenide (GaAs) and germanium have been studied by photoemission spectroscopy. Where possible, these interfaces were then tested electrically after the formation of capacitor structures. Each system presents its own unique challenges in the drive to the ultimate goal of developing smaller, faster and lower powered devices. On silicon substrates, an in-situ analysis of hafnium oxide grown by micro e-beam deposition in an oxygen atmosphere on an ultra-thin SiO2 buffer layer was carried out using XPS and synchrotron radiation. The self-limiting growth of an interfacial hafnium silicate layer was observed and the substrate temperature during the hafnium oxide depositions was found effect the onset temperature of hafnium silicide formation during post-deposition anneals. Hafnium oxide has also been grown ex-situ on silicon substrates by e-beam deposition in an oxygen atmosphere. The affects of an argon plasma ion assisted deposition technique (used in the growth of optical coatings to aid in film densification) and the oxygen back pressure on the growth of an interfacial oxide region were investigated by XPS. On gallium arsenide substrates, the elimination of anomalous frequency dispersion of the accumulation capacitance of GaAs high dielectric constant (high-κ) MOS devices by the use of a passivating silicon interfacial layer has been investigated. It has typically been assumed that this affect is due to a high interface state density and associated Fermi level pinning which is avoided by utilizing a high-κ/Si interface instead of the high-κ/GaAs interface. The surface treatment prior to silicon deposition is shown here to be a critical step in reducing this effect. Samples with and without frequency dispersion of the accumulation capacitance but with equally high interface state densities are presented, indicating that interface state density may not be the sole cause of the frequency dispersion of the accumulation capacitance. On germanium substrates, the use of a GeON based high-κ dielectric was investigated, as the water soluble native oxide of germanium has been shown in many works to be stabilised by the addition of nitrogen. A preliminary characterisation study of the interfacial quality of the GeON/Ge system is presented. Hafnium germanate has shown promise on silicon and here it has been analysed, with XPS and UPS on germanium substrates with 3 interfacial layers previously reported in the literature.