A new technique has been developed to grow semiconductor grade diamond substrates with dimensions comparable to those of currently available Si wafers. Previously, the synthetic single crystal diamond that could be grown measured only a few millimeters across, compared with single crystal Si substrates which typically are 10 to 15 cm in diameter. In the technique described, an array of features is first etched in a Si substrate. The shape of the features matches that of inexpensive, synthetic faceted diamond seeds. A diamond mosaic is then formed by allowing the diamond seeds to settle out of a slurry onto the substrate, where they become fixed and oriented in the etched features. For the experiments reported, the mosaic consists of seeds ∼ 100 μm across on 100 μm centers. A mosaic film is obtained by chemical vapor deposition of homoepitaxial diamond until the individual seeds grow together. Although these films contain low angle (<1°) grain boundaries, smooth, continuous diamond films have been obtained with electronic properties substantially better than those of polycrystalline diamond films and equivalent to those of homoepitaxial single crystal diamond films. The influence of growth conditions and seeding procedures on the crystallographic and electronic properties of these mosaic diamond films is discussed.