MANUFACTURE OF SEMICONDUCTOR INTEGRATED CIRCUIT DEVICE

摘要

PURPOSE:To simplify a process for forming a twin well on a semiconductor substrate. CONSTITUTION:After p-type impurity ions are implanted into the entire surface of a semiconductor substrate 1, photoresist 4 covering a region for forming p-type well is masked and n-type implurity ions are implanted selectively into the semiconductor substrate 1 of the n-type well formation region and the semiconductor substrate is heat-treated to extend and diffuse the n-type impurity and p-type impurity. After that, with the photo,resist 4 as a mask, the surface of the semiconductor substrate 1 is partially etched to form an alignment mark 5.