A novel processing sequence for the formation of gated diamond field emitter array (triode system) is proposed and the feasibility is tested by investigating the field emission property. The processing scheme is based on the selective deposition of diamond by using the well established nucleation enhanced process on substrate, so called bias enhanced nucleation (BEN). The structure of substrate was patterned [SiO2/Mo(Sate)SiO2(insulator)Si(100). Our preliminary results show that the diamond field emitter is turned on at around 87 V/mu m with the current level of about several mu A.