PURPOSE: To lower the defect level of a photoelectric conversion device so as to reduce the occurrence of dark currents by forming an area having the minimum forbidden width and another area having the maximum forbidden width in such a way that either one of the areas is deposited after the other area is deposited and plasma-treated with a gas containing fluorine.

CONSTITUTION: After an electrode 101 and electric charge injection prohibitive layer 102 are formed on a glass substrate 100, a final-stage carrier multiplying layer 107 is deposited on the layer 102. After depositing the layer 107, the discharge of electric charges and supply of a gaseous starting material are stopped. Then the surface of an area having the minimum forbidden width in the layer 107 is fluorinated by introducing a gas containing at least fluorine and restarting the discharge of electric charges. After fluorination, the discharge of electric charges and supply of the gas are stopped. Thereafter, a first graded layer 111 is deposited by forming the area having the maximum forbidden width of the layer 111. By plasma-treating the surface of the area having the minimum forbidden width composed of, for example, amorphous SiGe of the graded layer 111, the multiplication factor is improved and the occurrence of dark currents is reduced.