| 摘要 |
PROBLEM TO BE SOLVED: To reduce the number of fabrication steps by performing isolation without forming a buried layer when a DMOS transistor is formed in a second conductivity type semiconductor layer on a first conductivity type semiconductor substrate. SOLUTION: A second conductivity type impurity region 13 functioning as a drain is formed on a semiconductor substrate 10, a first conductivity type semiconductor layer 30 having impurity concentration higher than that of the semiconductor substrate 10 is formed on the semiconductor substrate 10 and the second conductivity type impurity region 13, and a second conductivity type semiconductor layer 20 is formed on the first conductivity type semiconductor layer 30. Impurities in the second conductivity type impurity region 13 are diffused to the first conductivity type semiconductor layer 30, and the second conductivity type impurity region 13 is extended to the first conductivity type semiconductor layer 30, and connected with the second conductivity type semiconductor layer 20. Thereafter, first conductivity type impurities are introduced into the second conductivity type semiconductor layer 20 located above the periphery of the second conductivity type impurity region 13, thus forming first conductivity type isolation regions 24c and 24d being connected with the first conductivity type semiconductor layer 30. COPYRIGHT: (C)2008,JPO&INPIT
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