Abstract
This review discusses within a unified framework various phenomena occurring in thermally grown 
films on silicon with hydrogen as the most important contaminant or additive. The possible sources of hydrogen are (i)
in the oxidizing ambient, deliberately introduced or resulting from permeation through hot furnace tubes, (ii) hydrogen in the room ambient oxide film on silicon, and (iii) deliberate or unintentional 
or 
in the ambient of postoxidation heat‐treatments. The "critical oxide thickness," which separates the linear oxidation regime from the parabolic one, is a very sensitive indicator of 
present in the oxidizing ambient. There is plenty of evidence, both direct and indirect, of hydrogen in 
films. In particular, infrared spectroscopy shows that OH and 
groups are present whose concentration and distribution depend strongly on preparation conditions. These groups can be H‐bonded to an oxygen; this feature and the presence of
distinguishes 
films from fused 
which is another form of non‐crystalline
. The H‐bonded OH groups in grown 
films may be preferentially aligned along structural channels and responsible for various transport processes characterized by ∼0.3 eV activation energy. Hydrogen greatly affects the properties of the 
interface, particularly its behavior under negative bias stress and irradiation. In fact, practically all properties of 
interface structures depend so strongly on hydrogen that its proper control and the understanding of its complicated role are probably the most important problems associated with these structures. This is particularly true for silicon‐based chemical sensors whose operation is basically determined by hydrogen in the 
film. Various aspects of the hydrogen in 
interface structures are similar to the role of hydrogen in 
and 
polymer films as well as in passivating films on metals.