MANUFACTURE OF SEMICONDUCTOR DEVICE

PROBLEM TO BE SOLVED: To provide the formation method of a shallow trench element separation area provided with superior electrical characteristics. SOLUTION: This manufacture is provided with a process for successively forming a first thermally oxidized film 2 and a silicon oxynitride film 3 on a semiconductor substrate 1 and etching the silicon oxynitride film 3 and the first oxidized film 2, so as to have the semiconductor substrate 1 partially exposed, the process for forming a groove 6 on the exposed semiconductor substrate 1, the process for thermally processing the semiconductor substrate 1 and forming a second thermally oxidized film 7 on the semiconductor substrate 1 inside the groove 6, the process for forming a CVD oxidized film 8 so as to fill at least the groove 6 on the semiconductor substrate 1, the process for chemically mechanically polishing the CVD oxidized film 8 with the silicon oxynitride film 3 as a stopper, the process for removing the silicon oxynitride film 3 and the process for removing the first thermally oxidized film 2.