An inertial electrostatic confinement fusion device modeling has been carried out. Finite element method is used in a 3D media in order to identify the potential and electrical fields inside the device. The effects of different materials on the electrostatic features are found. In addition, different geometric arrangements for cathode sphere (i.e. inner grid) are considered for the determination of spatial potential and electrical field. The effects of dielectric materials such as porcelain and polystyrene as the cathode holder have also been explored. It is found that porcelain giving a minimal potential value at the center of inner grid in order to confine ions. Increase in number of vertical rings on the inner grid diminishes the bottom corner of electrical potential, thereby ions are scattered to the entire region of the inner grid, thereby, an optimal shape for the inner grid can be adjusted for a better ion core at the middle of the grid for the confinement.