MANUFACTURING METHOD FOR SEMICONDUCTOR DEVICE

摘要

PURPOSE: In manufacturing an LDD (lightly doped drain) transistor with a dual gate oxide film, improve the hot-carrier character of an element by reducing the lateral field of the element by forming the overlapping part of an LDD area around the thick gate oxide film and a smaller gate. CONSTITUTION: Form the first insulating film and the second insulating film on the isolated semiconductor substrate (21) of the first active area and the second active area. The first insulating film (23) is thicker than the second insulating film (24). The first gate (25) and the second gate (26) are formed on the first gate insulating film and the second gate insulating film. Form the first gate lateral wall (28) on the first gate lateral surface thicker than the second gate lateral wall (30) on the second gate lateral surface. Form a low-density impurity area by injecting impurity ion with low-density on the whole surface of a substrate (21). Form the third gate lateral wall on the first gate lateral surface and the surface of the first gate lateral wall and form the forth gate lateral wall on the surface of the second gate lateral surface. Form a doped source/drain (35) with a high-density by injecting high-density impurity ion on the whole substrate (21) and by diffusing it. Thus a transistor with different threshold voltage is manufactured.