Hello All,
 I am trying to simulate/extract gate resistance of nmos device (IBM 90nm). technology uses BSIM4 model which models gate resistance in two components namely  intrinsic input impedance (Rii,bias dependent) and polysilicon gate resistance.

1. I am measuring S parameters of the device with Spectre by doing .sp analysis (figure attached,set up shown for BJT but it is same for MOS)

2. Spectre gives Y parameters and Real{Y11}=w^2*Cgg^2*Rg. Thus Rg can be extracted.[Ref http://www.silvaco.com/tech_lib_TCAD/simulationstandard/2000/jan/a1/a1.html]

3. BSIM4 literature suggests that Rg decreses as Vgs increases but I am observing opposite results.

I am not sure what mistake I am making. is my setup correct? Please let me know if you have any other method of extracting gate resistance.

Also output parameters of spectre gives value of rgbi and rgbd, spectre manual lists both of them as gate bias dependent resistor. But I am not sure what it is,is it the gate resistance??

As you can see I am very confused please help.

Thanks