Abstract: A Maximum Areal Density Recessed Oxide Isolation (MADROX) process for forming semiconductor devices, in which forms an insulating layer is formed on a monocrystalline silicon substrate and a patterned polycrystalline silicon-containing layer is formed on the insulating layer. The substrate is then subjected to a low temperature plasma assisted oxidation to form recessed oxide isolation areas in the exposed regions of the substrate, with minimal encroachment under the patterned polycrystalline silicon-containing layer. The patterned polycrystalline silicon-containing layer acts as a mask, without itself being oxidized. Low temperature recessed oxide isolation regions may thereby be formed, without "bird's beak" formation. Maximum Areal Density Bipolar and Field Effect Transistor (MADFET) devices may be formed, using the patterned polycrystalline silicon-containing layer as a device contact if desired.