Cadence tsmc 130nm (question) !

I'm using Cadence with tsmc 130nm technology file ... and it's my first time ... now I'm facing a weird problem i have built a very simple circuit (an NMOS with its drain connected to the gate in series with an ideal current source between VDD and GND) I'm trying to apply the famous saturation current formula to get the process parameters (uCox & lamda )

the problem : the saturation current formula is not applicable .. and it gives wrong results !