Patent ID: 6927116

Claim:
A method for manufacturing a semiconductor device, comprising: implanting first conductivity type impurity ions and second conductivity type impurity ions through a first area exposed by a first mask and into a first well forming region of a semiconductor substrate of a first conductivity type, said first conductivity type impurity ions constituting a first well and being shallower than the second conductivity type impurity ions; masking, by a second mask, at least a portion of the first area exposed by the first mask; implanting additional impurity ions of said second conductivity type through a second area exposed by the second mask and into a region around said first well forming region, said additional second conductivity type impurity ions and said second conductivity type impurity ions implanted below the first conductivity type impurity ions constituting a second well and activating said first conductivity type impurity ions and said second conductivity type impurity ions to form the first well and the second well in said semiconductor substrate.