Based on hydrodynamic energy transport model, the short channel effect immunity in deep sub-micron grooved-gate PMOSFET is studied and the influences of substrate and channel doping density on this effect immunity are also studied. At the same time, the results are compared with those of corresponding conventional planar devices. The investigated results show that the short channel effect can be depressed deeply for grooved-gate devices in deep sub-micron and super-deep sub-micron regions and with the increase of substrate and channel doping density, the threshold voltage rises and short channel effects are diminished. But the variation of threshold voltage in grooved-gate devices is smaller than that in planar devices. In the end, the results are explained based on the interior physics mechanism in these devices.