The present invention provides a method for preparing an ion optical device. A substrate is fabricated with a hard material adapted for a grinding process, the substrate at least including a planar surface, and including at least one insulating material layer. Next, one or more linear grooves are cut on the planar surface, to form multiple discrete ion optical electrode regions on the planar surface separated by the linear grooves. Then, conductive leads are fabricated on other substrate surfaces than the planar surface and in a through hole inside the substrate, to provide voltages required on ion optical electrodes. By using high-hardness materials in cooperation with high-precision machining, higher precision and a desired discrete electrode contour can be obtained.