Field-emission devices with a novel self-focusing gate structure using carbon nanotubes as emitters have been fabricated. Without additional focusing electrodes, the self-focusing gate structure employed a pair of gate electrodes parallel with the vicinity of emitters, which resulted in an asymmetric emission area as compared with the conventional gate structure. Therefore, electrons emitted from the emitters gave rise to an overlapping region on the anode plate so that a reduction of spot size had been achieved. According to the simulation results and luminescent images, this self-focusing gate structure had good control of the trajectory of electrons and therefore showed a smaller luminescent spot size than the conventional one. This gate structure, which utilizes a simple fabrication process, has the advantages of low-cost manufacturing and large-area scalability, and therefore is promising for application in field emission displays.