A diamond Schottky diode comprises an electrically conductive substrate 1 e.g. of silicon, a multi-layer structure of a semiconducting diamond layer 2 and an insulating diamond layer 3, and a metal electrode 4 e.g. of Al. The diode has a greater potential barrier under a reversed bias and hence exhibits better rectifying characteristics with a smaller reverse current. An ohmic electrode 5 of copper is attached with silver paste to the substrate 1. The diamond layers are deposited by CVD and the layer 2 is doped with boron. <IMAGE>
