In this paper, the growth kinetics and electrical properties of ultrathiii silicon-dioxide layers are reviewed. Topics discussed here include the onset of oxide growth, the effects of temperature, substrate orientation, dopant type and concentration, and stress on oxide growth kinetics. The use of in situ real-time ellipsotnetry to control the rapid-thermal oxidation of silicon will be presented. The electrical properties of the ultrathin silicon-dioxide layers will he discussed, especially the contact potential difference in MOS devices mid its dependence on the processing history and substrate orientation which will be explained in terms of the role of partial-charge-transfor dipolos at the oxide/silicon interface. Finally, gate tunneling considerations in MOSFET design, modeling, characterization, and circuit performance will be briefly presented. Copyright The Electrochemical Society.