A method of precisely controlling the thickness of dielectric islands on a substrate is provided. The subject method comprises forming a patterned layer of an etchable metal over a first dielectric layer on a substrate, forming a second layer of dielectric material thereover so that there is contact where the etchable metal layer has been removed, patterning the second dielectric layer so that islands remain only over the openings in the etchable layer, removing the etchable metal layer and then patterning the first dielectric layer. There are thus provided islands of dielectric material on the substrate having a thickness equal to the first only or the first and second dielectric layers together, respectively. The process may be extended to form at least one additional layer of dielectric material on certain of the islands.