Method for manufacturing a semiconductor device having a triple-well

Abstract

A method of manufacturing a semiconductor device having a triple-well structure, includes the steps of: forming a first well layer of a second conductivity type by implanting, as a first ion implantation, impurity ions of the second conductivity type to a specific depth from the surface of a semiconductor substrate of a first conductivity type and then subjecting the semiconductor substrate to an annealing treatment; forming a second ion-implanted region by implanting, as a second ion implantation, impurity ions of the second conductivity type into an end portion of first well layer with a specific width and at a depth from the surface of the semiconductor substrate to the surface of the first well layer to surround the first well layer; forming a third ion-implanted region by implanting, as a third ion implantation, impurity ions of the first conductivity type into a portion of the semiconductor substrate surrounded by the first well layer and the second ion-implanted region and at depth from the surface of the semiconductor surface to the surface of the first well layer; forming a second well layer and a third well layer by an annealing treatment of the second ion-implanted region and the third ion-implanted region after the second ion implantation and the third ion implantation respectively, or after the third ion implantation simultaneously.