A method of filling a depression of a workpiece is provided. The method includes forming a first thin film made of a semiconductor material substantially not containing an impurity along a wall surface which defines the depression, forming an epitaxial region conforming to crystals of the semiconductor substrate from the semiconductor material of the first thin film moved toward a bottom of the depression by annealing, etching the first thin film remaining on the wall surface, performing gas phase doping upon the epitaxial region, forming a second thin film made of a semiconductor material substantially not containing an impurity along the wall surface, further forming an epitaxial region from the semiconductor material of the second thin film moved toward the bottom of the depression by annealing, and performing gas phase doping upon the second thin film remaining on the wall surface and the epitaxial region.