| 摘要 |
PURPOSE:To make it possible to control a capacitance when a high voltage is applied, by diffusing impurities from a semiconductor substrate based on the measured value of the impurity concentration distribution in the depth direction in a semiconductor layer, and introducing the impurities from the surface part of the substrate. CONSTITUTION:On an N<+> type semiconductor substrate, an N<-> type epitaxial layer is grown, and voltage and capacitance characteristics are measured. The impurity concentration distribution in the depth direction from the semiconductor substrate to the epitaxial layer is accurately measured by an MOS method and the like. Based on the measured results, the diffusion of the impurities from the semiconductor substrate by heating and the like, the computed value of the P-type introduced impurities implanted from the surface of the substrate and the like are adjusted. Thus the impurity concentration is controlled. Then, a P-N junction of the impurity layer having a desired concentration is formed at a specified position in the epitaxial layer. Thus the capacitance can be controlled not only at the time when a low voltage is applied, but also at the time when a high voltage is applied. |
