| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device which is provided with a gate insulation film having no deterioration of characteristic, due to mixed impurities applied during ion implantation and its production method. SOLUTION: An LOCOS film 2 for separating regions Rn and Rp to form NMOSFET and PMOSFET is formed, and after a protection oxide film 25 has been formed, a first resist film Pr 41 in which the upper side of the region Rn is made open is formed thereon. Ions are implanted twice by using the first resist film Pr 41 as a mask, so as to form a threshold value control layer 10, as well as a P<-> -layer 18 for punch-through stopper, etc., and the protective oxide film 25 is etched to be removed by using the first resist film Pr 41 as a mask, and then the first resist film Pr 41 is removed. After the region Rp is treated in the same manner, a gate oxide film 27 is formed. Thus, mixed impurities applied during ion implantation are prevented from being diffused in the periphery during removal of a resist film, thereby improving the characteristic of gate oxide film.
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