Patent ID: 6198152
Filing Date: 2001-03-06
Classification: H01L

Abstract:
A semiconductor device protecting an element region from contamination by an impurity entering from outside through a laser trimming link portion, comprising:a semiconductor substrate;an element forming P-type well provided in a surface of said semiconductor substrate and including said element region;an element forming N-type well provided in a surface of said semiconductor substrate and including said element region and formed of a retrograde well;a field oxide film formed in the main surface of said semiconductor substrate, for isolating an element region from another element region;a laser trimming link formed on said field oxide film;a laser trimming link portion N-well formed below said field oxide film and in the surface of said semiconductor substrate and formed of a retrograde well, the laser trimming link portion N-well further being completely electrically isolated from said element forming P- and N-type wells and preventing entrance of said impurity to said element forming wells;wherein both said element forming N-type well and said laser trimming link portion N-well have an impurity concentration profile with at least two concentration peaks when a depth into the surface of the semiconductor substrate is plotted on abscissa and an impurity concentration is plotted on ordinate, respectively,among said plurality of concentration peaks, a peak at the deepest point in the surface of said semiconductor substrate has a higher impurity concentration than the other peak or peaks,said peak at the deepest point has a concentration of an N type impurity of not less than 1.times.10.sup.17 atoms/cm.sup.3, andan excess concentration peak, which does not exist in said laser trimming link portion N-well, is buried near a surface of said element forming N-type well.