SIMOX, which stands for Separation by Implantation of Oxygen, is a process used to create an insulating layer between the layers of a bulk silicon wafer.

There are two essential stages of the process: ion implantation and annealing.

In the implantation stage, oxygen ions are implanted in the silicon wafer and react with the silicon to form silicon dioxide precipitates.

However, the implantation causes considerable damage to the wafer and the layer of silicon dioxide precipitates is not continuous.

Thus high-temperature annealing helps repair the damage and form the oxide precipitates into a continuous layer.

Now the silicon's quality is restored and the buried oxide (BOX) layer can act as a highly effective insulator.

As compared with other methods like bonded SOI, the SIMOX wafer technology is characteristic in that it can produce silicon layers with thickness 200 nm or less and with extremely good thickness uniformity as required for low power CMOS devices.