280
Compact Models for Integrated Circuit Design
R
W
L
g
eff
eff
sh gate
=
ρ ,
(7.50)
where:
W eff and L eff are the effective channel width and channel length of the
device, respectively
ρ sh,gate is the gate sheet resistance per square [Chapter 2, Section 2.2.5.3]. The
typical sheet resistance for a polysilicon gate ranges between 20 and
40 Ω per square and is significantly lower for silicide as well as for
metal stack processes
At high frequencies, the accurate modeling of the gate resistance is very
complex due to the distributed transmission-line effect. Therefore, a lumped
equivalent gate resistance α times the end-to-end gate resistance given in
Equation 7.50 is used such that [56]
R
W
L
g
g eff
eff
sh gate
=
α
ρ ,
(7.51)
where:
α g = 1/3 to account for the distributed RC effects when the gate electrode
is contacted at one end and α g = 1/12 when the electrode is contacted
on both ends [57]
It is found that the distributed RC effect of the gate as well as the NQS effect,
that is, the distributed RC effect of the channel, affects the high-frequency
characteristics of MOSFET devices. Therefore, an additional component of
gate resistance must be considered to account for the distributed RC effect in
the channel or NQS effect. Thus, at high-frequency operation of a MOSFET
device, the distributed channel resistance seen by the signal applied to the
gate also contributes to the effective gate resistance in addition to the resistance of the gate electrode. Then the effective gate resistance consists of two
parts: the distributed gate electrode resistance (R g,eltd ) and the distributed
channel resistance seen from the gate (R gch ), as shown in Figure 7.8 [58].
R
R
R
g eff
g eltd
g ch
,
,
=
+
(7.52)
Typically, R g,eltd is insensitive to bias and frequency and, therefore, is obtained
from the gate electrode sheet resistance (ρ sh,geltd )
R
W
L
g eltd
s h geltd
g
,
,
=
+
ρ
α
β
(7.53)
where:
α g is 1/3 when the gate terminal is brought out from one side and 1/12
when connected on both sides
Compact Models for Integrated Circuit Design
R
W
L
g
eff
eff
sh gate
=
ρ ,
(7.50)
where:
W eff and L eff are the effective channel width and channel length of the
device, respectively
ρ sh,gate is the gate sheet resistance per square [Chapter 2, Section 2.2.5.3]. The
typical sheet resistance for a polysilicon gate ranges between 20 and
40 Ω per square and is significantly lower for silicide as well as for
metal stack processes
At high frequencies, the accurate modeling of the gate resistance is very
complex due to the distributed transmission-line effect. Therefore, a lumped
equivalent gate resistance α times the end-to-end gate resistance given in
Equation 7.50 is used such that [56]
R
W
L
g
g eff
eff
sh gate
=
α
ρ ,
(7.51)
where:
α g = 1/3 to account for the distributed RC effects when the gate electrode
is contacted at one end and α g = 1/12 when the electrode is contacted
on both ends [57]
It is found that the distributed RC effect of the gate as well as the NQS effect,
that is, the distributed RC effect of the channel, affects the high-frequency
characteristics of MOSFET devices. Therefore, an additional component of
gate resistance must be considered to account for the distributed RC effect in
the channel or NQS effect. Thus, at high-frequency operation of a MOSFET
device, the distributed channel resistance seen by the signal applied to the
gate also contributes to the effective gate resistance in addition to the resistance of the gate electrode. Then the effective gate resistance consists of two
parts: the distributed gate electrode resistance (R g,eltd ) and the distributed
channel resistance seen from the gate (R gch ), as shown in Figure 7.8 [58].
R
R
R
g eff
g eltd
g ch
,
,
=
+
(7.52)
Typically, R g,eltd is insensitive to bias and frequency and, therefore, is obtained
from the gate electrode sheet resistance (ρ sh,geltd )
R
W
L
g eltd
s h geltd
g
,
,
=
+
ρ
α
β
(7.53)
where:
α g is 1/3 when the gate terminal is brought out from one side and 1/12
when connected on both sides