An extreme-ultraviolet light source device comprises: a discharge chamber of which the inside is maintained in a vacuum; an electron beam-emitting unit which is located inside the discharge chamber and produces electron beams; and a metal radiator which is located inside the discharge chamber and is ionized by the electron beams. Extreme-ultraviolet radiation occurs in plasma generated from the metal radiator. The electron beam-emitting unit comprises: a cathode electrode; a plurality of emitters located on the cathode electrode and including a carbon-based material; and a gate electrode which is located on the plurality of emitters at a distance therefrom and to which a pulse voltage is applied.

The present invention provides an emitter capable of emitting electrons highly efficiently and stably for a long period of time, an electron gun and electronic apparatus using the emitter, and a method for manufacturing the emitter. An emitter equipped with a nanoneedle formed of a rare earth oxide represented by the general formula REO.sub.x (wherein RE is a rare earth element and 1x<1.5) is manufactured by carrying out a process of oxidizing the surface of a metal containing a rare earth element to form a film composed of a rare earth oxide represented by the general formula REO.sub.x (wherein RE is a rare earth element and 1x<1.5) and a process of working the film composed of the rare earth oxide into a needle shape using a focused ion beam.