The vertical transistor, however, does not rely on lithography and etching to define its gate length.

ECONOMIST: Transistors: A tall story | The

If this (topdown) manufacturing process is to be based on the most modern forms of deposition (including epitaxy), e-beam or ultra-deep UV lithography and precision etching, the mainstay of microelectronics and optoelectronics fabrication, then there are strict limits described below for which one-off fabrication is possible, but manufacture is not.

FORBES: Are There Physical Limits to Nanotechnology?