The selective epitaxial growth of InP was studied using atmospheric MOVPE. The selective embedded growth of the mesa stripe and the calculation of the diffusion equation around the mesa stripe were performed. In addition to the facet growth of the {111}B planes, the diffusion process of the source species in the vapor phase is a dominant factor in controlling the shape in the vicinity of the mesa. To achieve planar selective growth of the mesa stripe, the use of a SiO2 mask with eaves on the top of the mesa is effective. This suppresses the anomalous growth at the top of the mesa as predicted from the calculations. A mesa height of less than 3 μm was found to be essential to planar growth. A high-performance planar InGaAsP/InP buried heterostructure laser was successfully fabricated using this process.