The purpose of this work is to mathematically justify the phenomena of the plasma sheath formation near the surface of a ball-shaped material immersed in a bulk plasma, and to get some qualitative information of such a boundary sheath layer. To this end, we employ the Euler-Poisson equations in the three dimensional annular domain to investigate the existence, time-asymptotic behavior and quasi-neutral limit of the boundary layer solutions. This is a joint work with C.-Y. Jung (UNIST) and M. Suzuki (Nogoya Inst. Tech.).