Depending on what type of MOSFET you
are needing and what your voltage levels are will
determine what kind of model parameters you will be
needing. For instance, if it is for large voltages (>5 V)
you will be needing a different type of MOS with different
parameters than one which is less than 5 V.
don't know much about higher voltage FETs, but for <5 V
applications an okay place to start is through the MOSIS
web site (www.mosis.org
They keep a detailed list of SPICE parameters for
different size technologies (from 1.2um CMOS down to 90nm)
with different runs so that you can see the process
variations. As far as needing an ft of greater than 20
GHz, you will need to use at least 0.35um CMOS. Even then,
it may be pushing the limits.
If you can't find
the information you need on the MOSIS site, you can always
check foundry web sites. Sometimes they post their SPICE
parameters there for older processes and you can see if
they are in the ballpark that you are in.