MANUFACTURING METHOD OF SEMICONDUCTOR DEVICE AND SEMICONDUCTOR DEVICE

摘要

An improvement is provided in a manufacturing yield of a semiconductor device including transistors in which gate insulating films have different thicknesses. After a high-breakdown-voltage insulating film is formed over a silicon substrate, a surface of the high-breakdown-voltage insulating film is abraded for a reduction in the thickness thereof so that a middle-breakdown-voltage insulating film is formed to be adjacent to the high-breakdown-voltage insulating film. The high-breakdown-voltage insulating film is formed by a thermal oxidation method so as to extend from an inside of the main surface of the silicon substrate to an outside thereof. The middle-breakdown-voltage insulating film is formed so as to be thinner than the high-breakdown-voltage insulating film. The high-breakdown-voltage insulating film is formed as the gate insulating film of a high-breakdown-voltage MIS transistor, while the middle-breakdown-voltage insulating film is formed as the gate insulating film of a middle-breakdown-voltage MIS transistor.