multiple threshold

Typically this would be achieved by using different transistor models for the different transistors - but you do have an instance parameter called delvto on bsim3v3, bsim4, and several transistor models which allows you to specify a shift in the zero-bias threshold voltage.

So maybe that's what you want?

Andrew.

 Thankyou for your reply ,but  from where  can  i find  bsim3v3, bsim4  in virtuoso?

There aren't specific components in any Cadence-supplied library for bsim3v3 or bsim4 models. In general you'd have a symbol in your process design kit where you can enter the relevant parameters on the instances, and then refer to a model where you have model parameters defined.

There is nmos4 and nbsim4 (and similar p devices) in analogLib, but neither of these have delvto as a parameter that gets netlisted. That would be easy enough to achieve by copying the component and then editing the base CDF to add delvto as a parameter, and then changing the spectre simulation information in the CDF for these components to netlist delvto. If that's too hard, please contact customer support.

Details on the device models themselves (in the simulator) can be found by using "spectre -h bsim4" or "spectre -h bsim3v3".

Kind Regards,

Andrew.