To gain an understanding of the effect the addition of H,S has on sulfur-doped diamond growth, we focused on how the smoothness of the growing surface varied with the addition of H2S. We found that the distance between the plasma and the surface, i.e., the interaction between the plasma and the growing surface, influenced the effect the addition of H2S had on surface smoothness. The substrate temperature also influenced the effect the H2S had on surface smoothness. We were able to find a key factor to increasing the amount of the active carrier in sulfur-doped diamonds.