[en] We report on the electrical characteristics of in situ deposited Si₃N₄/Si/In_0.53Ga_0.47As depletion-mode metal-insulator-semiconductor field-effect transistors (MISFETs). MISFETs with 2.2-μm gate lengths fabricated by a self-aligned gate process exhibited extrinsic transconductances of over 200 mS/mm. The drain current drifted by only 1% during the first 10 h of operation. This small shift is attributed to the reduction of traps at the interface by a pseudomorphic Si layer, incorporated at the interface between the dielectric and the In_0.53Ga_0.47As channel