In this letter， an In_0.53Ga_0.47As/In_0.52Al_0.48As InP-based HEMT with f_T > 400 GHz was designed and fabricated successfully. A narrow gate recess technology was used to optimize the parasitic resistances. The gate length is 54.4 nm， and the gate width is 2 × 50 μm. The maximum drain current I_DS.max is 957 mA/mm， and the maximum transconductance g_m.max is 1 265 mS/mm. The current gain cutoff frequency f_T is as high as 441 GHz and the maximum oscillation frequency f_max reaches 299 GHz， even at a relatively small value of V_DS = 0.7 V. The reported device can be applied to terahertz monolithic integrated amplifiers and other circuits.