Abstract: The electric field in a miniaturized low energy electron gun, used for IC chip fabrication and comprising the complicated cathode/grid/anode structures held at specific potentials, were mathematically formulated with 2D hybrid mesh model, theoretically analyzed and numerically simulated in finite element method for the e-gun design optimization. The influence of the e-gun structures and models on the e-beam spot/current/trajectory was investigated. The simulated results show that the grid/anode distance, grid-aperture and grid potential all have a major impact. For example, as the grid/anode distance increases, the e-beam current/amplification decrease; as the grid-aperture increases, the e-beam magnification decreases and the e-beam current gradually increases to saturation.In addition, an increasing grid-potential slowly de-focuses the e-beam and steadily increases the e-beam current to saturation.