A gate-recessed AlGaN/GaN high electron mobility transistor (HEMT) on sapphire substrate having fmax of 200 GHz is reported. The gate-recessed device with a T-shaped gate exhibits a maximum drain current density of 1.1 A/mm, and a peak value of 421 mS/mm for extrinsic transconductance with minimum short-channel effects because of an InGaN back-barrier layer. A unity current gain cut off frequency(fT) of 30 GHz and a maximum oscillation frequency(fmax) of 105 GHz were obtained. After removing SiN by wet etching, the fT of the device increase from 30 GHZ to 50 GHz and the fmax increases from 105 GHz to 200 GHz, which are the results of lower Cgs and Cgd after removing of Si3N4.