| 摘要 |
PROBLEM TO BE SOLVED: To realize a high withstand voltage and low on-resistance DMOS- structured device, having a tall and gentle step shape of an oxide film sandwiched between a conductive plate and a silicon substrate used in a high breakdown voltage semiconductor device. SOLUTION: The semiconductor device manufacturing method comprises thermally oxidating a silicon substrate 1 to form a first silicon oxide film 10 on a silicon substrate 1, forming a second silicon oxide film 11 by chemical vapor deposition, forming phosphorus ion implantion regions 14 on the surface of the second silicon oxide film 11, forming a mask layer 3, and dipping in a solution containing hydrofluoric acid to etch the second and first silicon oxide films 11, 10 one after the other, thereby exposing the silicon substrate 1 surface. The slope angle of the oxide film steps can be controlled, by changing the dose of phosphorus ions in the phosphorus ion implanting regions 14.
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