solid state vs tubes

http://www.irf.com/technical-info/appnotes/mosfet.pdf

Capacitive turnon / turnoff delay.....that seems to be the issue.....
However, In a device with VERY thin gate ox......How much capactance are we actually talking about?

I never even heard the test guys talk about this.....

Fabguy do u need a hp4062ux to test at wafer probe?

I'm not a probe guy. i spent about 30 years making both ICs and discrete.
I am most familiar with probe parametrics as they apply to my area of specialty.

As for probers, I know they weren't HP. The last ones I remember were some kind of european 4 station from one central computer/data gatherer. Individual histograms of each wafer were stored for later analysis...patterns of failure and such. I avoided probe....looked too much like work.
I am much more comfortable with diffusion / implant / metalization and was very good at metrology. Nanometrics equipement, surface profile stuff and elipsometer along with various 4pt probe and specialty tools.

Magfan, here's a nice nutshell explanation that touches on this subject.

That there are capacitive elements of semiconductors should not come as a surprise to anyone- most tuners these days do not rely on variable capacitors to tune the station, instead they use variactor diodes, which take advantage of this capacitive element. Literally by changing the voltage (and thus forward current) on the device the capacitance changes and is useful as a tuning cap in the RF front end of the tuner.

Here's the link for the MOSFET capacitances (you can find many others on this site):

http://www.diyaudio.com/forums/tubes-valves/155106-ss-followers-drive-power-tubes-3.html#post2316318

Atmasphere, how is this "non-linearity" measured, and at what level does it become an issue?