The amount of silicon consumed by the formation of silicon dioxide is also fairly predictable from the relative densities and molecular weights of Si and SiO₂, i.e., the thickness of silicon consumed is 44% of the final thickness of the oxide formed. Thus, an oxide that is 1000 angstroms thick will consume about 440 angstroms of silicon from the substrate. In another words, 1µm thick Si oxidizes to 2.17 µm thick SiO₂.

Thermal oxidation is accomplished using an oxidation furnace which provides the heat needed to elevate the oxidizing ambient temperature. A furnace typically consists of a temperature controlled heating system, fused quartz process tubes, arrange for controlled flow of various gases. The heating system usually consists of several heating coils that control the temperature around the furnace tubes. The wafers are placed in quartz glassware known as boats. A boat can contain many wafers. The oxidizing agent (oxygen or steam) then enters the process tube through its source end, subsequently diffusing to the wafers where the oxidation occurs.

During dry oxidation, the silicon wafer reacts with the ambient oxygen, forming a layer of silicon dioxide on its surface. In wet oxidation, the water is heated in the 40-80°C range and oxygen or nitrogen carrier gases are used for the flow of water vapors to the chamber. Alternatively hydrogen and oxygen gases are introduced into a torch chamber where they react to form water molecules, which are then made to enter the reactor where they diffuse toward the wafers. The water molecules react with the silicon to produce the oxide and another byproduct, i.e., hydrogen gas.