(I suppose that you mean supercritical state of fluid.)
Supercritical state of liquid-gas is a state that liquid state and gas state stop to exist at particular temperature and pressure.
There is only just fluid state which has both liquid and gas property and if you change the pressure or temperature just a bit, it will change to one of the state.
How to achieve supercritical state ?
The supercritical state is done at HIGH TEMPERATURE and PRESSURE.
For example, the famous CO2 fluid (used to separate caffeine from the coffee bean) is acquired at 304.1 Kelvin and 72.8 atm.