Spice Syntax



Additional Information

More details can be found in the HyperSpice chapter in Extended Definitions for Advanced Users and Spice for Activate Users.


M1 24 2 0 20 TYPE1 

M31 2 17 6 10 MODM L=5U W=2U 

M1 2 9 3 0 MOD1 L=10U W=5U AD=100P AS=100P PD=40U PS=40U

The MOSFET transistor also called MOS is a Metal Oxide Semiconductor Field Effect Transistor. It is the most used inside the microelectronic field and is the based component for logic gates definitions.

ND, NG, NS, and NB are the drain, gate, source, and bulk (substrate) nodes, respectively.

MNAME is the model name.

L and W are the channel length and width, in meters.

AD and AS are the areas of the drain and source diffusions, in . Note that the suffix U specifies microns (1e-6 m) and P square-microns (1e-12 ).

If any of L, W, AD, or AS are not specified, default values are used. The use of defaults simplifies input file preparation, as well as the editing required if device geometries are to be changed.

PD and PS are the perimeters of the drain and source junctions, in meters.

RD and NRS designate the equivalent number of squares of the drain and source diffusions; these values multiply the sheet resistance RSH specified on the .MODEL control line for an accurate representation of the parasitic series drain and source resistance of each transistor.

PD and PS default to 0.0 while NRD and NRS to 1.0.

OFF indicates an (optional) initial condition on the device for dc analysis. The (optional) initial condition specification using IC=VDS, VGS, VBS is intended for use with the UIC option on the .TRAN control line, when a transient analysis is desired starting from other than the quiescent operating point. See the .IC control line for a better and more convenient way to specify transient initial conditions. The (optional) TEMP value is the temperature at which this device is to operate, and overrides the temperature specification on the .OPTION control line. The temperature specification is ONLY valid for level 1, 2, 3, and 6 MOSFETs, not for level 4 or 5 (BSIM) devices.


SPICE provides several MOSFET device models, which differ in the formulation of the I-V characteristic. The variable LEVEL specifies the model to be used. The models are declared using the syntax:
At least for a MOS model the user should select the level number. For this he has to choose among the following models:
Level number Mos type
0, 1 Mos Level 1
2 Mos Level 2
3 Mos Level 3
13 Bsim1
39 Bsim2
49, 53 Bsim3 v3.3(.2)
The DC characteristics of the level 1 through level 3 MOSFETs are defined by the device parameters VTO, KP, LAMBDA, PHI and GAMMA.

These parameters are computed by SPICE if process parameters (NSUB, TOX, ...) are given, but user-specified values always override.

VTO is positive (negative) for enhancement mode and negative (positive) for depletion mode N-channel (P-channel) devices. Charge storage is modeled by three constant capacitors, CGSO, CGDO, and CGBO which represent overlap capacitances, by the nonlinear thin-oxide capacitance which is distributed among the gate, source, drain, and bulk regions, and by the nonlinear depletion-layer capacitances for both substrate junctions divided into bottom and periphery, which vary as the MJ and MJSW power of junction voltage respectively, and are determined by the parameters CBD, CBS, CJ, CJSW, MJ, MJSW and PB.

Charge storage effects are modeled by the piecewise linear voltages-dependent capacitance model proposed by Meyer. The thin-oxide charge-storage effects are treated slightly different for the LEVEL=1 model. These voltage-dependent capacitances are included only if TOX is specified in the input description and they are represented using Meyer's formulation. There is some overlap among the parameters describing the junctions, e.g. the reverse current can be input either as IS (in A) or as JS (in A/). Whereas the first is an absolute value the second is multiplied by AD and AS to give the reverse current of the drain and source junctions respectively. This methodology has been chosen since there is no sense in relating always junction characteristics with AD and AS entered on the device line; the areas can be defaulted. The same idea applies also to the zero-bias junction capacitances CBD and CBS (in F) on one hand, and CJ (in F/) on the other.

The parasitic drain and source series resistance can be expressed as either RD and RS (in ohms) or RSH (in Ω/sq.), the latter being multiplied by the number of squares NRD and NRS input on the device line.

SPICE level 1, 2, 3 parameters:

name parameter units default example
1 LEVEL model index - 1
2 VTO zero-bias threshold voltage (VT0) V 0.0 1.0
3 KP transconductance parameter A/ 2.0e-5 3.1e-5
4 GAMMA bulk threshold parameter () 0.0 0.37
5 PHI surface potential () V 0.6 0.65
6 LAMBDA channel-length modulation 1/V 0.0 0.02
MOS1 and MOS2 only    
7 RD drain ohmic resistance Ω 0.0 1.0
8 RS source ohmic resistance Ω 0.0 1.0
9 CBD zero-bias B-D junction capacitance F 0.0 20fF
10 CBS zero-bias B-S junction capacitance F 0.0 20fF
11 IS bulk junction saturation current (IS) A 1.0e-14 1.0e-15
12 PB bulk junction potential V 0.8 0.87
13 CGSO gate-source overlap capacitance F/m 0.0 4.0e-11
per meter channel width  
14 CGDO gate-drain overlap capacitance F/m 0.0 4.0e-11
  per meter channel width  
15 CGBO gate-bulk overlap capacitance F/m 0.0 2.0e-10
per meter channel length  
16 RSH drain and source diffusion Ω/q 0.0 10.0
sheet resistance    
17 CJ zero-bias bulk junction bottom cap. F/ 0.0 2.0e-4
per sq-meter of junction area  
18 MJ bulk junction bottom grading coeff. - 0.5 0.5
19 CJSW zero-bias bulk junction sidewall cap. F/m 0.0 1.0e-9
per meter of junction perimeter  
20 MJSW bulk junction sidewall grading coeff. - 0.50(level1)  
21 JS bulk junction saturation current A/ 1.0e-8
per sq-meter of junction area  
22 TOX oxide thickness meter 1.0e-7 1.0e-7
23 NSUB substrate doping 1/cm3 0.0 4.0e15
24 NSS surface state density 1/c 0.0 1.0e10
25 NFS fast surface state density 1/c 0.0 1.0e10
26 TPG type of gate material: - 1.0
+1 opp. to substrate  
-1 same as substrate  
0 Al gate    
27 XJ metallurgical junction depth meter 0.0 1
28 LD lateral diffusion meter 0.0 0.8
29 UO surface mobility c/Vs 600 700
30 UCRIT critical field for mobility V/cm 1.0e4 1.0e4
degradation (MOS2 only)  
31 UEXP critical field exponent in - 0.0 0.1
mobility degradation (MOS2 only)  
32 UTRA transverse field coeff. (mobility) - 0.0 0.3
(deleted for MOS2)  
33 VMAX maximum drift velocity of carriers m/s 0.0 5.0e4
34 NEFF total channel-charge (fixed and - 1.0 5.0
mobile) coefficient (MOS2 only)  
35 KF flicker noise coefficient - 0.0 1.0e-26
36 AF flicker noise exponent - 1.0 1.2
37 FC coefficient for forward-bias - 0.5
depletion capacitance formula  
38 DELTA width effect on threshold voltage - 0.0 1.0
(MOS2 and MOS3)  
39 THETA mobility modulation (MOS3 only) 1/V 0.0 0.1
40 ETA static feedback (MOS3 only) - 0.0 1.0
41 KAPPA saturation field factor (MOS3 only) - 0.2 0.5
42 TNOM parameter measurement temperature C 27 50
For more information on models see also the Berkeley device models documentation.