| 摘要 |
PURPOSE:To accomplish a high-speed responding operation of the titled element by a method wherein the specific resistance of an epitaxial layer is set low on the side of substrate (the lower part) which gives an influence upon the storage time of minority carrier, and the specific resistance is set high on the surface side (the upper part) which inflicts an influence on the junction capacitance of a photo diode, thereby enabling to cut down both junction capacitance of the photo diode and and the storage time of the minority carrier. CONSTITUTION:Among the epitaxial layers 12 of a circuit (bipolar IC) built-in light-receiving element, the thickness of the upper epitaxial layer 12a is set at the value or thereabout which is obtained by adding the component of a depletion layer extended on the side of the epitaxial layer 12 of a photodiode to the depth of diffusion of a P<+> diffusion layer 11. The junction capacitance of the photo diode part is determined by the upper epitaxial layer 12a having large specific resistance, and the storage time of minority carrier is determined by the lower part epitaxial layer 12b having small specific resistance. The storage time of carrier is reduced by the lower epitaxial layer 12b, and the junction capacitance of the photo diode part is also reduced by the upper epitaxial layer 12a. |
