文档介绍：Device Modeling for Analog and RF CMOS Circuit Design.
Trond Ytterdal, Yuhua Cheng and Tor A. Fjeldly
Copyright 2003 John Wiley & Sons, Ltd.
ISBN: 0-471-49869-6
1
MOSFET Device Physics
and Operation
INTRODUCTION
A field effect transistor (FET) operates as a conducting semiconductor channel with two
ohmic contacts – the source and the drain – where the number of charge carriers in the
channel is controlled by a third contact – the gate. In the vertical direction, the gate-
channel-substrate structure (gate junction) can be regarded as an orthogonal two-terminal
device, which is either a MOS structure or a reverse-biased rectifying device that controls
the mobile charge in the channel by capacitive coupling (field effect). Examples of FETs
based on these principles are metal-oxide-semiconductor FET (MOSFET), junction FET
(JFET), metal-semiconductor FET (MESFET), and heterostructure FET (HFETs). In all
cases, the stationary gate-channel impedance is very large at normal operating conditions.
The basic FET structure is shown schematically in Figure .
The most important FET is the MOSFET. In a silicon MOSFET, the gate contact
is separated from the channel by an insulating silicon dioxide (SiO2) layer. The charge
carriers of the conducting channel constitute an inversion charge, that is, electrons in the
case of a p-type substrate (n-channel device) or holes in the case of an n-type substrate
(p-channel device), induced in the semiconductor at the silicon-insulator interface by the
voltage applied to the gate electrode. The electrons enter and exit the channel at n+ source
and drain contacts in the case of an n-channel MOSFET, and at p+ contacts in the case
of a p-channel MOSFET.
MOSFETs are used both as discrete devices and as active elements in digital and
analog monolithic integrated circuits (ICs). In recent years, the device feature size of
such circuits has been scaled down into the deep submicrometer range. Presently, the
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