thermal noise of a resistor

When we model thermal noise of a resistor, to be delivered thermal noise power kTB, load resistance and source resistance are matched. So noise source voltage has square root 4kTRB(R is matched resistance).

And in Mosfet when we model thermal noise of channel resistance, as you know channel resistance of mosfet is 1/gm. So it is decribed as attached image.


we model thermal noise voltage source to deliver kTB at load.
But in case of mosfet thremal noise modeling, I cannot find that mechanism. It just add noise source current. Why..?

I am confused that. Please help me