In the case of highly negative biased target immersed in the plasma, the current on the target is composed of the incident ion current and the emission electron current. The virtual area of collecting current on the target is proportional to the sheath area formed over the target electrode which is considerable increased with applied high bias. The spatially distributed plasma also affects on the sheath formation, resulting in the target current. Consideration of the dimensional sheath formation and spatial plasma distribution with the secondary electron emission coefficient is conducted for analyzing the target current. Experiments were carried out with the planar stainless steel and aluminum targets having a diameter 100mm, negatively bias ranging in 2kv-11kV. Sheath size and spatial plasma distributions are measured by electrical probes. The current model including the dimensional sheath, spatial plasma distribution and secondary electron emission coefficient will be presented.