Re: Scattering parameters...
If you can not find S-Params because most foundaries sometimes do not give them all the times except when transistors are employed in RFIC's, Amplifiers, Mixer etc. This is a sad fact.
Even in this case these parameters then can be entered as whole in what is the design itself.
For transistors sometimes , watch out: they give always: VBIC, Gummel-Poon, and BSIM3 and BSIM4, TOM3 models.
Check to find these. These in most of the cases are in datasheets. They are ok to substitute S-Parameters.
djalli