new method to fabricate silicon field emitter array (FEA) by forming porous silicon is proposed. Silicon FEAs have been successfully fabricated on n-type and p-type substrates using this method. In this method, porous silicon is formed around the masking discs in HF solution to make tips. Then the porous silicon is thermally oxidized to form the insulator between the gate metal and the silicon substrate. The final gate hole diameter is nearly equal to the masking disc diameter, and the gate leakage current is less than 0.5% of the anode current. For a silicon FEA made on an n-type substrate with a gate hole diameter of 1.4 mu m and for a silicon FEA made on a p-type substrate with a gate hole diameter of 1.8 mu m, an emission current of 1.1 mu A per tip and 1.0 nA per tip is obtained at a gate voltage of 100 V, respectively.