| 摘要 |
PURPOSE:To obtain a P-N junction diode in which a capacity variation rate becomes 1/2 or higher over the entire range of reverse bias voltage by forming a circular region interior of low density of a high density region having the same conductive type, and forming the circular region exterior of a high density region having different conductive type. CONSTITUTION:A region I is an N<+> region of radius (a), a region II is an N<-> type regin of outer diameter (b), and a region III is a P<+> type region. The boundary surface between the regions II and III becomes the stepwise P-N junction surface. The impurity densities in the respective regions are constant in all regions. The capacity variation rate (m) can be represented by the equation, where l represents the distance from the center of the end of a depletion layer and l/b=x. Since always x=l/b<1 when a reverse bias voltage is applied, (m) becomes 1/2 or higher, and as the reverse bias voltage increases, the value of m becomes large, and the maximum value occurs in case of l=a, i.e., x=a/b. |
