GaAs pseudomorphic high electron mobility transistors recessed by electron cyclotron resonance (ECR) plasma etching have been investigated. We used a BCl3/SF6 gas mixture to implement the gate recess process. We obtained a uniformity of the threshold voltage to within 50 mV in 3-inch wafers. The GaAs PHEMTs with a 0.2-mu m gate length recessed by the ECR plasma exhibited a minimum noise figure (NFmin) as low as 0.26 dB with an associated gain (G(a)) of 13 dB at 12 GHz. At 18 GHz, the NFmin was 0.47 dB with a Ga of 11.66 dB. These results suggest that the ECR plasma etching process reported here is suitable as a manufacturing process for gate recess of a GaAs PHEMT.