Nanofabrication technique for 10 nm T gates in high electron mobility transistors(HEMTs)is the key to achieve THz speed in microwave/THz communications.Traditional fabrication process by electron beam lithography(EBL)in multilayer resist stack has found its limitation in foot-width around 30 nm due to proximity effect.Dry etch technique was then introduced to further shrink the foot-width down to sub 30 nm using a layer of dielectric layer such as SiNx or SiO2 as foot definition layer and even 10 nm using a resist layer as an etch mask.