Epitaxial Si/CaF2/Si(111) structures have been grown by molecular beam epitaxy. Planar and cross‐sectional transmission electron microscopy has been used for characterization of these structures. The CaF2 layer is high quality, single crystal material exhibiting type B epitaxy with respect to the Si substrate. On the other hand, the Si overgrowth layer consists of a mixture of crystallites which are aligned either with the Si substrate or with the CaF2. The defect density in the overgrown Si improves with distance from the interface with the CaF2. Variation of the substrate temperature during growth has relatively little effect on the quality of the epitaxial Si.