SEMICONDUCTOR DEVICE HAVING MULTI-GATE INSULATION FILM AND MANUFACTURING METHOD THEREOF

摘要

PURPOSE: A semiconductor device is provided to ensure high reliability by minimizing the upper surface step of gate insulation films having thicknesses different from each other. CONSTITUTION: A plurality of active areas(1a,1b) are restricted to certain area of a semiconductor substrate(301), and constituted by the first active area(1a) having the surface lower than that of the semiconductor substrate(301) and the second active area(1b) having the surface higher than that of the first active area(1a). The first gate insulation film(305a) is formed on the first active area(1a). The second gate insulation film(305b) is formed on the second active area(1b), and has a thickness smaller than that of the first gate insulation film(305a). An element isolation area(307) is formed among the active areas(1a,1b), and has the bottom lower than that of the first active area(1a). An element isolation film(309) fills the element isolation area(307), and covers the whole side walls of the first gate insulation film(305a) and second gate insulation film(305b).