We have developed a novel subquarter micron gate fabrication process without any electron beam (EB) lithography techniques or phase shift (PS) methods. To fabricate a subquarter micron width mask, the process uses thinning line patterns of photoresist by O2reactive ion etching and the reversing of that resist by a thin Al film. We applied this process to fabrication of a pseudomorphic AlGaAs/InGaAs high electron mobility transistor. The device exhibited a peakgmof 715 mS/mm,fTof 95 GHz, andfmaxof 176 GHz. These results show this process to be a useful alternative to EB or PS techniques for subquarter micron gates.