To provide a manufacturing method of a semiconductor device capable of simply performing a separation of a lower-part electrode without damaging the lower-part electrode, and basically blocking a single bit fail generated when an auxiliary film is used.

A manufacturing method of a semiconductor device comprises the steps of forming an insulating film 27 having a plurality of open parts 28 for defining a lower-part electrode 29A of a capacitor on an upper part of a semiconductor substrate; forming a conductive film 29 on the insulating film 27 according to a shape of the open parts 28; and executing a separation of the lower-part electrode by quickly etching the conductive film 29 at a part outside the open parts 28 rather than the inside the open parts 28; wherein a mixed gas of a first gas which enters vertically for physical etching, and a second gas having a good chemical reaction with the conductive film due to a plasma state for chemical etching, is used, and a bias power is adjusted so that a physical etching at a bottom part in the open parts can be minimized. By including the step of performing the separation of the lower-part electrode 29A, a process cost can be remarkably reduced.