| 摘要 |
PURPOSE:To prevent a punch-through current, to abruptly rise VG-IDS characteristic, and to prevent thermal runaway by forming a region to which a concentration first conductivity type impurity lower than the impurity concentration of a second conductivity type well layer and higher than the impurity concentration of a first conductivity type semiconductor substrate in the well layer on a substrate. CONSTITUTION:A P-well region 21 is formed on an N-type semiconductor substrate 1, and an N-type impurity region 25 having higher impurity concentration than that of an N-type region 1b and lower impurity concentration than that of the region 21 is formed at a position in contact with N<+> type source regions 4a, 4b in the region 21. In a channel region 24, since the N-type impurity of the region 25 is higher than that of the region 1b but lower than the P-type impurity concentration of the region 21, its conductivity type is of P-type. The peak of the P-type impurity concentration near the source end of the region 21 is reduced, and the gradient of the impurity concentration becomes substantially flat. |
