PURPOSE: To grow a semiconductor crystal layer of high purity and preferable quality by providing a liquid nitrogen shroud disposed at a position near the surface to be brown with a semiconductor crystal in a semiconductor substrate for trapping contaminant gas exhausted from a heater.

CONSTITUTION: A liquid nitrogen shroud 6 is disposed near a heater 7 in a substrate heater holder 16. The shroud 6 near the heater 7 protrudes from the crystal growing surface of a semiconductor substrate 9 to a molecular beam cell 4, and formed near in the degree of not forming a shade to the molecular beam irradiated to the substrate 9. The shroud near the holder 16 and the shroud near the molecular beam are integrated. Thus. a space for performing a crystal growth is narrowed, a space and the heater 7 of a contaminant gas exhaust source are separated by the shroud 6, and the gas is trapped by the shroud 6, thereby growing a crystal layer of high purity and preferable quality.