Nanometer-scale silicon field emitters with the high packing density have been fabricated successfully by using a self-organized selective oxidation technique. The diameter at the bottom of each nanoemitter was 20-30 nm, and its height was 3-5 nm. The density was approximately 3-5 x 10(11) tips/cm(2). Emission characteristics were measured in a diode structure without gate electrodes for simplicity. As a result, it was found that the field emission current was detected at much lower anode voltages than conventional cone-shaped Si emitters. The apex shape was dependent on the oxidation conditions, and the emission current was dependent on the microscopic tip shape. It is expected that the field is significantly enhanced by the nanoprotrusions.