Patent ID: 6048770
Filing Date: 2000-04-11
Classification: H01L

Abstract:
A method of manufacturing a nonvolatile semiconductor memory device comprising the steps of:forming a source region and a drain region of a second conductivity type on a main surface of a semiconductor substrate of a first conductivity type by ion-implanting impurity of the second conductivity type into said semiconductor substrate to define a channel region;forming a first impurity region of the second conductivity type under at least said entire drain region by ion-implanting impurity of the second conductivity type into said semiconductor substrate, said first impurity region having an impurity concentration lower than that of said drain region; andforming a second impurity region of the first conductivity type under at least said first impurity region under said drain region by ion-implanting impurity of the first conductivity type into said semiconductor substrate with an implantation angle not more than 8.degree. with respect to a direction perpendicular to said main surface of said semiconductor substrate, wherein the second impurity region of the first conductivity type does not extend to the main surface of the semiconductor substrate.