| 摘要 |
<P>PROBLEM TO BE SOLVED: To uniform a gate oxide film on a boundary near the surface of an NWELL between the NWELL and a DWELL and on a channel region. <P>SOLUTION: The gate oxide film (104a) is formed on the NWELL (102) in advance. Then, on the gate oxide film, a stepped mask (130a) with a level difference in thickness which consists of a thick portion and a thin portion is formed. With the thick portion as a mask, impurity ions for the DWELL (122) are implanted into the NWELL (102). Then, with the whole mask including the thick portion and the thin portion as a mask, impurity ions for source/drain regions are implanted. Thereafter, the dopants are thermally diffused to simultaneously form a DWELL diffusion layer (122), a source diffusion layer (124), and a drain diffusion layer (126). <P>COPYRIGHT: (C)2004,JPO |
