Electronic Devices and Circuits Engineering Sciences 154

References:

It may be helpful to reprise some of the very nice lectures entitled Principles of Semiconductor Devices (local fragment) by Bart Van Zeghbroeck from the University of Colorado.

See also the notes entitled Metal Oxide Semiconductor (MOS) Capacitor from MIT course 6.152J/3.155J - Microelectronics Processing Technology (local copy)  and the notes entitled Field-Effect Devices: The MOS Capacitor from the University of Wisconsin course ECS 135/1 (local copy)

The MOS Capacitor

Freeze frames from the SUNY-Buffalo applet Electrostatics of MOS Capacitor

(source)(local copy)

Freeze frames from the SUNY-Buffalo applet MOS Capacitor with Bias
(click on images to enlarge)

Note how the "metal" type influences the band structure under various bias conditions.  In particular note that inversion is possible in the equilibrium state (zero gate-source voltage) and that the threshold voltage may be either positive or negative.

	"Metal" = p+ poly silicon	"Metal" = n+ poly silicon	"Metal" = aluminum
Equilibrium Condition
Flat-band Condition
Threshold Condition

Another Energy Band View of MOS Capacitance

click image to enlarge                                          (source)

The MOS Inversion Layer Charge (local copy)

(source) (local copy)

Now see Large and Small Signal Models of MOSFET Operation