| 摘要 |
PURPOSE:To enable the arbitrary selection of a Zener voltage regardless of the impurity concentration in an epitaxial layer by the constitution in which the second semiconductor region has a formation depth which is different from those of an element isolation region and a base region. CONSTITUTION:An anode region 3b of a Zener diode is formed by diffusion separately from a diffusion layer 4 for element isolation. Namely, a formation depth of the region 3b is different from that of the isolation region 4 and further different from that of a base region (not shown in the drawing). Accordingly, the impurity concentration of the anode region 3b can be selected arbitrarily and a Zener voltage can be designed regardless of the thickness and the impurity concentration of an epitaxial layer 2 thereby increasing the degree of freedom of design substantially. For example, if the impurity concentration of the anode region 3b is increased, the Zener diode of a low voltage can be obtained and a good low voltage characteristics and a good temperature characteristics can be obtained. Also, if the Zener diode of a high voltage is necessary, it can be achieved easily. |
