silvaco simulation with athena atlas

tylerli

I have a question about silvaco athena && atlas simulation, MOS structure, when I gate length is 0.6um, get Vth is 1.8V, but I only change gate length to 0.55um, get Vth is 1.6V, it's a error data I know, but I do not know why, what wrong with the program, how can I change it. would you please help about it. Very thanks!