This paper reports that the theoretical limit of the superjunction (SJ) structure is discussed with considering the charge imbalance margin. The SJ structure is attractive to reduce the specific on-resistance dramatically due to the charge compensation concept. The breakdown voltage, however, is lowered by the charge imbalance between n- and p-columns due to the electric field modulation. The analytical models of the theoretical on-resistance limit considered with the charge imbalance margin were provided in this work. The analytical results showed that the on-resistance reduction required not only lateral pitch narrowing but also the charge imbalance margin cut. This tendency can be confirmed from the experimental results in the previous works. The theoretical limit was estimated to be 7 mΩcm2 for 600 V-class SJ-MOS with the charge imbalance margin of 3%.