Exercise 8.1
The high-frequency C − V characteristic curve of a MOS capacitor is shown in Figure 1. The area of the device is 2 × 10−3 cm2. The metal-semiconductor work function difference is φms = −0.50 V, the oxide is SiO2, the semiconductor is silicon, and the semiconductor doping concentration is 2 × 1016 cm−3.
(a) Is the semiconductor n or p type?
(b) What is the oxide thickness?
(c) What is the equivalent trapped oxide charge density? (d) Determine the flat-band capacitance.
Figure 1: Figure for Problem 8.1
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Exercise 8.2
Consider the high-frequency C − V plot shown in Figure 2.
(a) Indicate which points correspond to flat-band, inversion, accumulation, threshold, and depletion modes.
(b) Sketch the energy-band diagram in the semiconductor for each condition.
Figure 2: Figure for Problem 8.2
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Exercise 8.3
A p-channel MOSFET has the following parameters: kp′ = 0.10 mA/V2, W/L = 15, and VT = −0.4 V. Calculate the drain current ID for
(a) VSG = 0.8 V,VSD = 0.25 V; (b)VSG =0.8V,VSD =1.0V; (c)VSG =1.2V,VSD =1.0V; (d)VSG =1.2V,VSD =2.0V.
Exercise 8.4
Consider a p-channel MOSFET with the following parameters: kp′ = 0.12 mA/V2 and W/L = 20. The drain current is 100μA with applied voltages of VSG = 0, VBS = 0, and VSD = 1.0 V.
(a) Determine the VT value.
(b) Determine the drain current ID for VSG = 0.4 V, VSB = 0, and VSD = 1.5 V. (c)WhatisthevalueofID forVSG =0.6V,VSB =0,andVSD =0.15V?
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Exercise 8.5
One curve of an n-channel MOSFET is characterized by the following parameters: ID(sat)=2×10−4 A,VDS(sat)=4V,andVT =0.8V
(a) What is the gate voltage?
(b) What is the value of the conduction parameter?
(c)IfVG =2VandVDS =2V,determineID.
(d)IfVG =3VandVDS =1V,determineID.
(e) For each of the conditions given in (c) and (d), sketch the inversion charge density
and depletion region through the channel.
Exercise 8.6
An NMOS device has the following parameters: n+poly gate, tox = 400 ̊A,Na = 1015 cm−3, and Q′ss = 5 × 1010 cm−2.
(a) Determine VT .
(b) Is it possible to apply a VSB voltage such that VT = 0 ? If so, what is the value of VSB ?
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Exercise 8.7
Draw the ID − VSD relationship for a p-type MOSFET at different gate voltages, as- suming the source is grounded. Explain why there is the saturation region, and how the saturation point changes with different gate voltages.
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Reference
1. Neamen, Donald A. Semiconductor physics and devices: basic principles. McGraw- hill, 2003.
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