The present paper reports the self-ordering behavior of rod-like and random-coiled poly(dialkylsilane)s with Si-H termini on HO-presented substrates. The effects of stiffness and molecular length of poly(dialkylsilane)s and substrates were investigated by a combination of quartz crystal microbalance, specular reflectance UV spectroscopy, and atomic force microscopy. A simple immersion of the HO-presented substrates into poly(n-decylisobutylsilane) (PDBS)/isooctane enabled the manipulation of cooperative structural phase transition from horizontal to almost vertical orientation to the substrate. Furthermore, the orientation behavior of vertically self-assembled PDBS depended on its molecular weight. On the other hand, a random-coiled poly(methyl-n-propylsilane) was only horizontally immobilized, resulting in the formation of a mushroom-like structure on HO-presented substrates. Knowledge gained from these studies may lead to a new, simple approach designed to fabricate vertically and/or horizontally self-assembled nanoarrays with rod-like and/or random-coiled semiconducting macromolecules onto solid surfaces.