Method for manufacturing semiconductor device using multiple ion implantation masks

A production method for a semiconductor device comprising the steps of:

• (a) providing a semiconductor substrate having a semiconductor layer of a first conductivity type formed on a surface thereof;
• (b) forming a first mask so as to cover a region of the semiconductor layer;
• (c) forming a well region of a second conductivity type by implanting impurity ions of the second conductivity type into the semiconductor layer having the first mask formed thereon;
• (d) reducing a thickness of the first mask by removing a portion of the first mask;
• (e) forming a second mask covering a portion of the well region by using photolithography;
• and
• (f) forming a source region of the first conductivity type by implanting impurity ions of the first conductivity type into the semiconductor layer having the first mask with the reduced thickness and the second mask formed thereon,
• the method further comprising, between step (d) and step (e),
• a step (h) of forming a sidewall formation film covering the first mask with the reduced thickness, wherein,
• step (e) includes
• a step (e1) of forming on the sidewall formation film a resist layer covering a portion of the well region, and
• a step (e2) of etching the sidewall formation film and the resist layer to form the second mask and the sidewall from the sidewall formation film;
• and
• step (f) is a step of forming the source region of the first conductivity type by implanting impurity ions of the first conductivity type into the semiconductor layer on which the second mask, the first mask with the reduced thickness, and the sidewall are formed.