| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device where the dispersion of the threshold voltage of a depression-type lateral MOSFET is small, concerning a semiconductor device which has a depression-type lateral MOSFET made within a well. SOLUTION: A p well 5 is formed in an N-type semiconductor substrate 1, and N-type impurities for deciding the threshold voltage of a depression-type lateral MOSFET are introduced into the P well 5 so as to form an N-type region 6. Then, the surface of the N-type region 6 is oxidized to form an oxide film 7b. By this oxidation, the depth of pn junction made between the P well 6 and the N-type region 6 becomes shallow. Then, the oxide film 7b is removed, and a gate oxide film and a gate electrode are made. The dispersion of the threshold voltage in the depression-type lateral MOSFET decreases by that the depth of the pn junction becomes shallow and besides the concentration of the impurities at the surface of the P well becomes low.
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