Method of manufacturing semiconductor device by forming first and second oxide films by use of nitridation

摘要

According to this invention, there is provided a method of manufacturing a semiconductor device. An element region and an element isolation region are formed on a semiconductor substrate of a first conductivity type. A first oxide film prospectively serving as a gate insulating film is formed in the element region. Thermal oxidization is performed after annealing is performed in nitrogen or ammonia atmosphere to nitrify an entire surface of the first oxide film. A predetermined region of a nitrified first oxide film is removed, and a second oxide film prospectively serving as a gate insulating film is formed in the predetermined region using the nitrified first oxide film as a mask. A gate electrode constituted by a polysilicon film is formed on each of the nitrified first oxide film and the second oxide film.