A 70 nm InAs channel quantum well field effect transistor (QWFET) fabricated by a narrowing source-drain (S/D) spacing technique was realized for future high-speed and logic applications. The S/D spacing was decreased from 3 to 0.65 mu m through a simple fabrication process, which is an ameliorative redeposition ohmic technique. The drain-source current density and transconductance of the device were increased from 391 to 517 mA/mm and from 946 to 1348 mS/mm after the scaling of the S/D spacing, respectively. In addition, the current gain cutoff frequency (f(T)) was also increased from 185 to 205 GHz. These results show that the easy method can effectively improve the III-V QWFET device performance for high-frequency and high-speed applications. (C) 2010 The Japan Society of Applied Physics