Patent ID: 7309629

Claim:
A method for fabricating a semiconductor device in which a semiconductor memory element having an ONO (silicon oxide layer/silicon nitride layer/silicon oxide layer) film as a gate insulating film and a semiconductor element in a CMOS part are formed on a semiconductor substrate, said method comprising: the step of forming an ONO film on the top surface of the semiconductor substrate; the step X of forming bit lines for the semiconductor memory element by introducing first impurities into parts of the semiconductor substrate; the step Y of forming bit line oxide films on the bit lines; the step of implanting second impurities into a region of the semiconductor substrate in which the semiconductor element in the CMOS part is to be formed; and the step of forming a thermal oxide film to be a gate insulating film on the region of the semiconductor substrate into which the second impurities have been implanted, wherein the steps X and Y are carried out after the step of forming said thermal oxide film.