This paper presents a benchmarking comparison between InAs FinFET and gate-all-around (GAA) MOSFET by a 3-D TCAD simulation. The complete FinFET fabrication process is demonstrated followed by a TCAD simulation platform based on the experimental data. Both DC and RF simulation results are shown here. Further optimizations are explored for InAs FinFET/GAA MOSFET through TCAD simulations. It is found that with optimizations in materials, device geometry and fabrication, significant enhancement in DC/RF performances is possible with these devices. In addition, GAA MOSFET shows a better potential for future RF application.