To decrease surface roughness of c-plane-oriented epitaxial MnSb films fabricated on Si (111) single crystal substrates, reduction of the optimum substrate temperature for formation of c-plane-oriented MnSb films was explored based on the results obtained from precise analyses of initial film growth of c-plane-oriented MnSb films. The main results are as follows: (1) during MnSb film deposition on the Si (111) substrate at Tsub. = 250°C, (a) with an initial layer of MnSb film less than 70 nm thick, Mn reacted with Si, resulting in formation of MnSi, and Sb re-evaporated; (b) with this film region thicker than 70 nm, MnSb was formed on MnSi; (2) the MnSi (111) epitaxial buffer layer played an important role in achieving c-plane-oriented MnSb grains on the Si (111) substrate; (3) by using two-step sputtering, which is a method for fabricating MnSb films on the MnSi layer after changing substrate temperature, (a) we reduced the substrate temperature for preparing the c-plane-oriented MnSb film from 250°C to 200°C, and (b) expanded the temperature range where c-plane-oriented MnSb grains were created, from 150°C to 230°C; and (4) the use of two-step sputtering at Tsub. = 150°C decreased the surface roughness of the film to Ra= 3.6 nm.