Improved methods and structures are provided for an array of vertical geometries which may be used as emitter tips, as a self aligned gate structure surrounding field emitter tips, or as part of a flat panel display. The present invention offers controlled size in emitter tip formation under a more streamlined process. The present invention further provides a more efficient method to control the gate to emitter tip proximity in field emission devices. The novel method of the present invention includes implanting a dopant in a patterned manner into the silicon substrate and anodizing the silicon substrate in a controlled manner causing a more heavily doped region in the silicon substrate to form a porous silicon region.