| 摘要 |
PURPOSE: To decrease the number of steps required for forming N well and P well regions by masking a P well region with photoresist after implanting branket boron and then making a hole in an N well region by silicon etching. CONSTITUTION: A silicon dioxide 11 is thermally deposited on the surface of a silicon substrate 12. The substrate 12 coated with an oxide is then implanted with P type impurities of boron, for example, without using any mask thus forming a P type material layer 21 on the substrate 12. The denuded oxide film 11 is then removed partially by subjecting a wafer to oxide etching and the substrate is trenched by about 1,000Åfrom the initial level by etching at a part not located directly under a photoresist 22. When the wafer is implanted with N type impurities, e.g. phosphor, the phosphor prevails residual boron over the entire expected N well region. Finally, the photoresist 22 is stripped and the water is subjected to high temperature diffusion in oxygen atmosphere.
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