A new combination of low/high/low sensitivity trilayer (PMMA/PMIPK/PMMA) resist system was used for deep UV lithography to fabricate submicron T-shaped gate. Gate length as narrow as 0.2 µm is achieved. The GaAs HEMT's with 0.3 µm T-shaped Ti/Pt/Au gate is fabricated using this technology. The HEMT demonstrated a 0.6 dB noise figure and 13 dB associated gain at 10 GHz. This deep UV lithography process provides a high throughput and low cost alternative to E-beam lithography for submicron T-gate fabrication.