Abstract: The present invention provides a process and apparatus for selectively depositing materials on a semiconductor device, such as depositing phosphors or other optical materials on a light emitting diode (LED), using an electrophoretic deposition process. The semiconductor device comprises a p-side and an n-side. A first biasing voltage is applied between an anode and the p-side of the semiconductor device. A second biasing voltage is applied between the p-side and the n-side of the semiconductor device. The relative biasing of the p-side and the n-side determines where coating is deposited on the semiconductor device. An optional pre-coating process is used to deposit a high resistivity dielectric material, such as silica, on the semiconductor device. The pre-coating can even the electric field on the surface of the semiconductor device, where local features such as metal connections or passivation layers disturb the electric field during phosphor deposition without pre-coating.