Local oxidation used to isolate two adjacent devices.

LOCal Oxidation of Silicon - oxidation of selected areas of a silicon wafer by masking off the oxidation reaction from other regions. A thin uniform silicon dioxide, SiO2, layer is initially formed and then a layer of silicon nitride, Si3N4, is deposited. The silicon nitride is photolithographically patterned and then a relatively thick silicon dioxide layer is grown in the openings in the silicon nitride. The silicon nitride blocks oxidation wherever silicon nitride is present. Following oxidation the silicon nitride layer is stripped off the wafer. The thin initial silicon dioxide layer is used to prevent stress from direct contact between silicon and silicon nitride. LOCOS is widely used to isolated MOSFETs with minimum linewidths 350nanometers.

Locos is an object oriented framework for building parsers and other language processing tools.