The hybrid lithography of a 280‐keV Si++focused ion beam (FIB) and a 20‐keV shaped electron beam (EB) has been applied to fabricate a mushroom‐shaped gate for a high electron mobility transistor. In this process, a resist in the gate region is reduced to ∼0.2 μm by an FIB lithography (corresponding to ‘‘top‐gate’’ formation), and then the center of the top gate is exposed by the EB (corresponding to ‘‘bottom‐gate’’ formation). For a thin resist, patterns with smaller dimensions are more easily delineated by an EB exposure than for a thick resist. A 0.2‐μm pattern can be obtained by using a shaped EB system with a high throughput. The radiation damage is neglected due to the use of EB for the bottom‐gate formation.