Patent ID: 7776660

Claim:
A method of manufacturing a semiconductor device, comprising the steps of: (a) forming a semiconductor element and interconnect on the side of a first surface of a semiconductor substrate of a first conductivity type; (b) after covering the semiconductor element and interconnect with a protective film, attaching a reinforcing plate over the protective film; (c) after the step (b), implanting first impurity ions from the side of a second surface which is on the side opposite to the first surface of the semiconductor substrate; (d) after the step (c), first laser irradiating a region into which the first impurity ions have been implanted to form a first semiconductor region of the first conductivity type having an activation ratio of the first impurity ions of 60% or greater and having an impurity concentration greater than an impurity concentration of the semiconductor substrate, such that the first laser irradiating is performed using a first wavelength and a first energy density; (e) after the step (d), implanting, from the second surface side of the semiconductor substrate, second impurity ions into a region shallower than the region into which the first impurity ions have been implanted; (f) after the step (e), second laser irradiating a region into which the second impurity ions have been implanted to form a second semiconductor region of a second conductivity type which is different from the first conductivity type and which has an activation ratio of the second impurity ions from 1 to 15%, such that the second laser irradiating is performed using the first wavelength and a second energy density lower than the first energy density; and (g) after the step (f), peeling off the reinforcing plate from the first surface of the semiconductor substrate.