The DC and RF characteristics of a 0.15 µm GaAs power metamorphic high electron mobility transistor (MHEMT) have been investigated and consequently, 77-GHz-band-low-noise-amplifier (LNA) millimeter-wave monolithic integrated circuits (MMICs) were fabricated using the 0.15 µm power MHEMT device. The 0.15 ×100 µm2 MHEMT device showed a drain saturation current of 40.4 mA/mm, an extrinsic transconductance of 857 mS/mm, and a threshold voltage of -0.64 V. For the distributions of DC characteristics across a 100 mm wafer, the standard deviation of the threshold voltage and the maximum extrinsic transconductance were -0.64 ±0.03 V and 810 ±25 mS/mm, respectively. The obtained cutoff frequency and maximum frequency of oscillation were 141 and 243 GHz, respectively. The 8 ×50 µm2 MHEMT device showed a 33.2% PAE, an 18.1 dB power gain, and a 50.1 mW output power at 5.8 GHz. A very low minimum noise figure of 0.79 dB and an associated gain of 10.56 dB at 26 GHz were obtained for the 0.15 ×100 µm2 MHEMT with an indium content of 53% in the InGaAs channel. This excellent noise characteristic is attributed to the marked reduction of gate resistance by the T-shaped gate with a wide head and the improved device performance. The fabricated LNA MMIC using a 0.15 ×100 µm2 MHEMT device exhibited a small signal gain of 20 dB and a noise figure of 5.5 dB at a frequency range of 76 to 77 GHz.