A method of forming a transistor can include forming a gate mask on a substrate having a vertical location aligned with that of a transistor control gate; implanting first conductivity type dopants with the gate mask as an implant mask to form a first shallow halo region; implanting first conductivity type dopants with at least the gate mask as an implant mask to form a first deep halo region having a peak dopant concentration profile at a greater substrate depth than the first shallow halo region; forming an epitaxial layer on top of the substrate; forming a first control gate structure on the epitaxial layer; and forming a first source or drain region, of a second conductivity type, in at least the epitaxial layer to a side of the first control gate, and over the first shallow halo region and the first deep halo region.
