This is with R=100ohm. You may see below the gate current is much higher (+/- 75mA in peaks) but it charges/discharges much faster. The gate current is most of the time zero..
Mind it is an simulation with a Mosfet model only, the generator is 25kHz 1:1, 10V, 100ns r/f edges.
Indeed, MOSFET gates aren't ideal capacitors by any means, the plateau is very evident in those traces.
In real life there's always ringing and other artifacts as well.
And, the talented students may calculate the total input gate capacitance from the above waveforms and their timings 
Thank you guys! Ill take a look at these!
That plateau is due to something called the Miller Capacitance or Miller Effect.
As I said, calling it Gate "capacitance" is a simplification.
