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Compact Models for Integrated Circuit Design
with impurities same as the well type, (3) halo implants with impurities same
as the well type, and (4) source-drain (S/D) engineering to implant S/D with
impurities opposite to the well-type. The channel engineering with V th adjust
implant produces vertically nonuniform channel doping profile and S/D
engineering with halo implants produces laterally nonuniform channel doping profile in advanced bulk MOSFET devices [7–11].
A MOSFET structure shown in Figures  4.1 and 4.2 can be characterized
by different circuit elements and current flow between source-drain terminals as shown in Figure 4.3. Figure 4.3a shows that a MOSFET structure
includes parasitic source, drain, and gate resistances R s , R d , and R g , respectively; and parasitic pn-junctions from body to source and from body to
drain [12]. Figure 4.3b shows the small signal capacitances associated with
a MOSFET structure. The capacitances include intrinsic source, drain, and
body capacitances C GS , C GD , and C GB , respectively, with reference to source
and the extrinsic gate overlap capacitances C GSO , C GDO , and C GBO with source,
drain, and body, respectively, with reference to the gate and the junction
capacitances C jS and C jD due to body to source and body to drain pn- junctions,
respectively, as shown in Figure 4.3b [13].
Source
pn-diode
Body
(a)
Drain
pn-diode
Drain
R d
R g
Gate
I g,leakage
Source R s
I ds
L
Gate
n+ Source
n+ Drain
V g
V s
C GSO
C GB
C GS C GD
C GDO
C JS
C JD
V b
Extrinsic region
Extrinsic region
Intrinsic region
(b)
p-Body
V d
FIGURE 4.3
Basic features of MOSFETs: (a) basic circuit elements and current flows and (b) intrinsic and
extrinsic parasitic capacitance elements.