On the transient operation of partially depleted SOI NMOSFET's

The transient operation of partially depleted (PD) Silicon-On-Insulator (SOI) NMOSFET's is investigated, based on two-dimensional numerical simulations. The studied devices have a gate length of 0.2 μm and a floating body. They are designed for a supply voltage of 2 V. In the case of gate transient, we show that the body voltage is more influenced by the capacitive coupling with the gate electrode than the impact ionization current. Further, we demonstrate, for the first time, that the anomalous subthreshold slope, that exists in a DC static transfer I-V curve, does not exist in fast transient mode because the minimum time constant for body charging by impact ionization current is on the order of 3 ns in such devices.