EMI noise of IGBT/IEGT (Injection Enhancement Gate Transistor) circuit is significantly reduced by introducing a new device design criterion. The design criterion improves dV CE /dt controllability during the IEGT turn-on transient without sacrificing the featured low saturation voltage of IEGT structure. The perfectly floating p-well region as the criterion prevents the undesirable V GE overshoot and the resultant uncontrollable dV CE /dt. The design criterion has been applied to a 1200V ultra thin PT-IEGT, and low noise turn-on characteristics have been experimentally obtained. IEGTs with the new criterion enable low noise operation and precise gate control, which are suitable for active gate drive.