| 摘要 |
PROBLEM TO BE SOLVED: To form an LDD region of a high breakdown voltage transistor which is longer in comparison with an LDD region of a MOS transistor driven by a low voltage symmetrically to a gate of the high breakdown voltage transistor without using a mask, when the low-voltage driven MOS transistor and a high breakdown voltage MOS transistor at the same time. SOLUTION: After a gate 108a of a high breakdown voltage transistor and a gate 108b of a transistor driven by a low voltage are formed, the implantation of phosphorus ions for an LDD is performed by using the gate 108a as a mask, followed by a heat treatment for diffusing phosphorus under the gate 108a to form an LDD layer 110. After that, a side wall 114a is formed on the side wall of the gate 108a and the high-density source and drain implantation is performed by using the side wall 114a as a mask. As a result, the LDD layer 110 which is longer than an LDD layer 112 of a low-voltage transistor can be formed symmetrically to the gate 108a without using a mask. Furthermore, downsizing of the high breakdown voltage transistor can be attained and variability of characteristics can be restrained.
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