Quiz and Homework
This page provides 3 quiz set and 3 homework question
1. Which of the following is NOT true ?
A. QOX is a function of applied gate voltage
B. Threshold voltage is a function of tox.
C. P+Poly silicon gate is usually used for n-MOS capacitor.
D. Once the threshold condition occurs, Qd (=the depletion charge) is not increased any more with Vgs.
2. Which of the following is correct ?
A. There is no electric field in the oxide in an equilibrated MOS capacitor.
B. For the threshold, Qch and Qd > 0 in an n-MOS capacitor.
C. In a flat-band condition, the surface potential Ys = 0
D. In accumulation, the depletion takes place in the silicon surface.
3. Which of the following is incorrect ?
An n-MOS (p-type) capacitor,
A. In flat-band condition, |Qg| = |Qox|, Qch = 0
B. In threshold condition, |Qg| + |Qox| = |Qch + Qb|
C. In flat-band condition, Qb = 0, Qch = 0
D. In threshold condition, |Qg + Qox| = |Qch|, Qb = 0
1. Once the inversion condition occurs, there is no further increase
of either the depletion layer width or the depletion charge. Explain the
reason of this phenomenon.
2. In a MOS capacitor, the threshold is defined when Ys
(surface potential) = 2YB
YB is X= Ei-Ef
value in the applet). (In fact, the condition is referred
to as the strong inversion case in a MOS device. And thus, a threshold
voltage for actual device has some deviation to that of a MOS capacitor,
and commonly it is measured by given conditions from the manufacturer ).
In an n-MOS capacitor (i.e. p-type MOS capacitor), if Na =1 x 1015cm-3
, and Al gate tox = 100A, ni = 1.45 x 10 10cm
Ys & YB
for the threshold. (Hint , Na= ni e (Ei-Ef)/kT at
T = 300 K)
3. In an n-MOS capacitor, the depletion layer width is Wd
= (2 esi Ys
/qNa)1/2 . If the threshold condition occurs, the depletion
layer width will reach its maximum value (Wdmax). Derive an
equation for Wdmax at Ys = 2YB
, and find the value for Wdmax using the same values for ni,
Na and T in Question 2.