Current drive enhancement by using high-permittivity gate insulator in SOI MOSFET's and its limitation

Speed enhancement effect by using high-permittivity gate insulator in SOI MOSFET and its limitation were investigated by two-dimensional device simulator and circuit simulator. The SOI structure is suitable to have excellent current drive by using high-permittivity gate insulator, Although the gate capacitance increases as a function of its dielectric constant, the current drive does not increase proportionally due to the inversion capacitance. According to the simulation results of the delay time, when the pulse waveforms driven by a CMOS inverter are propagated through 1mm-long interconnects, the delay time significantly reduces at the dielectric constant value of around 25 (Ta2O5). Thus, it is worthwhile using Ta2O5 for gate insulator to achieve high-speed operation, Furthermore, the reduction of source parasitic series resistance is a key issue to realize the highest current drive by using high-permittivity gate insulator in SOI MOSFET.