| 摘要 |
An improved varactor diode (40) is obtained by providing a substrate (70) having a first surface (73) and in which are formed a first N region (46) having a first peak dopant concentration (47) located at a first depth (48) beneath the surface (73), and a first P region having a second peak dopant concentration (50) greater than the first peak dopant concentration located at a second depth (51) beneath the surface less than the first depth (48), and a second P region (42) having a third peak dopant concentration (43) greater than the second peak dopant concentration and located at a third depth at or beneath the surface (73) less than the second depth (51), so that the first P region (49) provides a retrograde doping profile whose impurity concentration increases with distance from the inward edge (44) of the second P region (42) up to the second peak dopant concentration (50).
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