Abstract Formation of the supported planar bilayer of dipalmitoylphosphatidylcholine (DPPC) on SiO 2 surfaces modified with the self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS) has been investigated by atomic force microscopy (AFM). DPPC was deposited by the fusion of vesicles on SiO 2 surfaces with OTS-SAM islands of different sizes and densities. The DPPC bilayer membrane formed self-organizingly on the SiO 2 surface with small and sparse OTS islands, while did not when the OTS islands were larger and denser. The relative size between the vesicles and the SiO 2 regions is the critical factor for the formation of the DPPC bilayer membrane.