We present and characterize the first epitaxial Si/CuTnS(2) heterojunction devices. By means of molecular beam epitaxy (MBE), slightly copper-rich CuInS2 epilayers are deposited on sulphur-terminated Si-(1 1 1) surfaces of n-type wafers. Both the quality of the substrate and the deposited epilayer are controlled in situ using low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES) and various other methods including transmission electron microscopy (TEM) are applied in the ex situ structural characterization. The heterojunction diodes are completed by the deposition of an indium-tin oxide (ITO) layer and of metallic contacts. Their electronic and structural properties are discussed.