A metamorphic HEMT MMIC technology with 20 nm gate length is presented, developed for the fabrication of terahertz-wave monolithic integrated circuits (TMICs) with operational frequencies beyond 500 GHz. The MBE grown transistor heterostructure comprises a strained In _0.8 Ga _0.2 As channel with high electron mobility and high electron density for proper device scaling. The realized mHEMTs achieve a source resistance R _S of 0.1 Ωmm which is required to minimize resistive losses in combination with an extrinsic maximum transconductance g _{m_max} of 2500 mS/mm. The output characteristics of the 20 nm devices show no short channel effects and demonstrate sufficient pinch-off behavior for analog applications. For a transistor with 2 × 10 μm gate width a cut-off frequency f _T of 660 GHz was extrapolated which is to our knowledge the highest published f _T for any HEMT device. The presented 20 nm mHEMT technology was employed for the design of a compact four stage lownoise amplifier (LNA). The total small signal gain of the LNA exceeds 20 dB from 115 - 175 GHz.