Abstract: A method for forming a crystal layer including the steps of (1) supplying first impurity atoms onto a surface of a crystal substrate to form a surfactant layer adsorbed on the surface, (2) supplying nucleus atoms which bond with the first impurity atoms, (3) repeating step (2) until second impurity atoms are supplied in step (4), and (4) supplying second impurity atoms which bond with the first impurity atoms and the nucleus atoms to epitaxially grow a crystal layer including the nucleus atoms as a crystal nucleus material doped with the first and second impurity atoms. A co-dopant having a three-atom composite formed by supplying the atoms on the surface of the crystal enables smooth doping thereof to produce the crystal having the high density dopant or a low resistance.