In order to fabricate diamond microstructures, we have developed a site-selective microwave plasma chemical vapor deposition (MW-PCVD) method, which is based on the great difference, in the 106order, between the nucleation densities of diamond on Pt and SiO2 surfaces. First, we prepared a substrate consisting of a Pt film covered with a SiO2 layer on which holes of a 2 μm×2 μm square were fabricated by photolithography. Next, diamond was synthesized onto this substrate by MW-PCVD using a mixture of CH4 and H2 as a reaction gas. Under appropriate conditions, diamond crystals selectively nucleated in the holes where the Pt film surface was exposed, while the surrounding SiO2 surface remained undeposited. A microdiamond array was successfully fabricated by this method. Diamond crystals of ∼2 μm are precisely arranged at vertical and lateral intervals of 20 μm. © 1998 American Institute of Physics.