One of the most popular MOSFET technologies available today (and the only
one freely available to Canadian Universities) is the complementary MOS, or
CMOS, technology. This technology makes use of both P and N channel devices
in the same substrate material. Such devices are extremely useful, since
the same signal which turns on a transistor of one type is used
to turn off a transistor of the other type. This allows the design of
logic devices using only simple switches, without the need for a
pull-up resistor.
Figure 
shows a typical inverter implemented with this
technology, together with its switch equivalent.
Note that the substrate
connections are explicitly shown for each transistor. The substrate for the
N channel device is connected to ground, while that for the P-channel
device is connected to the positive voltage supply.
Figure
shows a typical cross-section for a device similar to the inverter shown in
Figure .
The CMOS device eliminates many of the problems of the NMOS devices; it
consumes no DC power (at least, for static logic) since there is never a
purely resistive path to ground; also, the pull-up and pull-down resistances of
the P- and N-channel transistors can be made equal, so the device has
a symmetric output. Of course, the technology is inherently more complex
than the NMOS technology, since two different types of transistors must be
made on the same substrate.
Figure
shows a set of transient output
characteristics for a typical CMOS inverter similar to that shown in
Figure ,
implemented with the Northern Telecom CMOS3 technology. This
technology is available to Canadian universities through the Canadian
Microelectronics Corporation. (In this example, the NMOS pull-down
transistor has the minimum channel length and width of 3 
, while the
PMOS pull-up transistor has a channel width of 6 
. The output load for
the inverter is another identical inverter, and the input is a
pulse with a 0.5 ns. rise and fall time. The results were obtained from a
SPICE simulation, with SPICE parameters obtained from CMC.)
