We propose a metal–oxide–semiconductor field-effect transistor (MOSFET)-structured Si field emitter array (FEA) with a ring gate FET. A ring-shaped MOSFET gate electrode surrounds the Si FEA and this electrode plays two roles. The first is to control the emission current, and the other is to focus the electron beam emitted from the FEA. The emission current can be controlled by the voltage of the ring gate. We evaluated focusing properties of the ring gate FET structured Si FEA by observing the emission patterns on an anode phosphor screen. The detailed electron trajectory simulation qualitatively agreed with the experimental results. The simulation revealed that the new device has better focusing properties than a conventional FEA with an in-plane lens electrode.