A method of forming islands that utilizes masking layers during implantation was used. Windows in the mask define the silicon island positions. In these regions the layer structure corresponds to the conventional SIMOX structure. However, in the mask region, where the oxygen ions loose part of their kinetic energy before reaching the silicon, the buried oxide is shifted towards the surface. The aim is to achieve total dielectric isolation by implantation and annealing only, thus avoiding a subsequent LOCOS or mesa etching step. New experimental parameters, which include masking material, mask thickness and the geometry of the bevel edge, determine the structural properties of the non-planar oxide as well as the surface topology. Polycrystalline silicon masks have been successfully used to form continuous non-planar buried oxide layers. Experimental results are briefly discussed.