A comprehensive analysis and performance comparison of CombFET and NSFET for CMOS circuit applications

The performance of comb-like channel field effect transistor (CombFET) and nanosheet FET (NSFET) is addressed at both device and circuit levels at the 3-nm node. The CombFET is realized by combining both FinFET and NSFET structures in the channel area. At the device level, the DC, analog/RF figures of merit (FOMs) are analyzed in detail. From simulations, it is observed that the on current (ION) is enhanced by 42% from NSFET to CombFET at the same off current (IOFF) of 250 pA under the same footprint (FP). CombFET's improvement over NSFET is the result of the channel's wider effective width. Further, an improvement of 30% in cut-off frequency (fT) and a decrement of 20% in intrinsic delay (tau) is noticed from NSFET to CombFET. On top of that dimensional impact on the electrical performance of CombFET analysed in detail. The CMOS circuit behaviour for ring oscillator (RO) is studied using the Verilog-A model for both FETs in the CADENCE tool. An oscillation frequency (fOSC) of 111.9 GHz and 82.7 GHz was noticed for CombFET and NSFET, respectively. Thus, the analyses demonstrate that CombFET offers superior performance over NSFET without increasing the FP.