Investigation of Symmetric Dual-k Spacer Trigate FinFETs From Delay Perspective

During recent years, high-k spacer materials have been extensively studied for the enhancement of electrostatic control and suppression of short-channel effects in nanoscaled devices. However, the exorbitant increase in fringe capacitance due to high-k spacers deteriorates the dynamic circuit performance that restricts researchers using these devices in high-performance circuits. For the first time, this paper demonstrates the usage of high-k spacer material with an optimized length for effective reduction of circuit delay and an improvement in robustness. An improvised symmetric dual-k spacer (SymD-k) underlap trigate FinFET architecture termed as SymD-k is employed for this purpose. From extensive 3-D simulations, this paper demonstrates that SymD-k device significantly improves overall circuit delay and robustness (noise-margins) with fully capturing the fringe capacitance effects. A CMOS inverter and a three-stage ring-oscillator (RO3) are adopted to carefully investigate the performances. In comparison with the conventional device, the SymD-k device speeds up the RO3 circuit by 27% and 33% using high-k spacer dielectric HfO₂ and TiO₂, respectively. However, a purely high-k FinFET device deteriorates the RO3 delay per stage up to 11%. Furthermore, the effect of underlap length and supply voltage on SymD-k-based RO3 delay over the conventional ones are also dealt in.