Field electron emitters with self-aligned volcano-type gate arrays were fabricated in order to generate an electron beam and their characteristics were measured. These devices were fabricated by reactive ion etching followed by successive forming of an insulating layer and deposition of a gate electrode. The self-aligned gate is achieved by reactive ion etching a planarizing resist film in 1:2 O-2/Ar plasma and high dc bias (200 V). The device presented here has a 0.4 mum gate opening. The fabrication technology and structural and electrical characteristics of a self-aligned volcano-type gate field emission triode emitter array are reported.