MANUFACTURE OF SEMICONDUCTOR DEVICE

PROBLEM TO BE SOLVED: To prevent a channel stopper from spreading to the periphery of a trench in an element isolation formed using the trench and to make the enhancement of an interelement isolation breakdown strength and a reduction in the capacity between an element formation region and a substrate possible. SOLUTION: A trench to reach at least a one conductivity type semiconductor substrate 1 is formed and a dielectric film 4 is formed under the bottom of the trench 3. Then, opposite conductivity type impurities are selectively ion- implanted in the substrate 1 through a trench open part and an opposite conductivity type impurity implanted region 5 is formed. At this time, the film 4 functions as a mask to the impurity ions and prevents the opposite conductivity type impurities from being implanted directly under the bottom of the trench 3 and in the vicinity of the trench 3. After the film 4 is removed, one conductivity type impurities are selectively ion-implanted in the substrate 1 through the trench open part. At this time, a condition that the amount of implantation in the opposite conductivity type impurity ion implantation becomes roughly same as the projection range of the impurity ions is selected and a channel stopper 6 is formed. A dielectric film 4a is buried in the interior of the trench 3 and the roughly flat surface of the substrate 1 is formed.