We report here an effective method for the fabrication of a large number of triode-type microgated carbon nanotube field emitter arrays. Our technique combines dual-beam focused ion beam technology and plasma-enhanced chemical vapor deposition, avoiding the tedious lithography and wet chemistry procedures conventionally used to fabricate such structures. Field emission testing revealed that increasing gate voltage by as little as 0.3 V had significant impact on the local electric fields, lowering the turn on and threshold fields by 3.6 and 3.0 V/microm, respectively. The field enhancement factor of the emitter arrays was also increased from 149 to 222. A quantum mechanical model for such triode-type field emission indicates that the local electric field generated by a negatively or positively biased gate directly impacts the tunneling barrier thickness and thus the achievable emitter current.