The apparatus and its preliminary results of gas source silicon molecular beam epitaxy are reported for the first time. In this study, silane (SiH4) was used as a source gas. A subchamber was designed to control the gas flow precisely. SiH4exposure during the initial cleaning was effective in lowering the cleaning temperature and saving the cleaning time. Epitaxial silicon films grew uniformly on 4‐in. wafers. There was no spitting defect on the epitaxial films. Moreover, selective epitaxial growth was realized using a patterned SiO2mask.