| 摘要 |
PROBLEM TO BE SOLVED: To provide a light receiving element with built-in circuit, comprising a photodiode, which reduces both junction capacitance and series resistance, with a response speed which is sufficiently fast. SOLUTION: An auto-doped layer 2, where the impurity concentration gradually decreases as recedes from the surface of a semiconductor substrate 1, and a lightly-doped layer 3 comprising such impurity concentration distribution as even in depth direction constitute a high specific resistance epitaxial layer 30, which is used to reduce the junction capacitance of a photodiode. W>2T, where W is the width of a P-type embedded diffusion layer 4, and T is the thickness of a P-type epitaxial layer 30, which is set so that the series resistance of the photodiode is reduced, even if the impurity concentration at the surface of an embedded isolation diffusion layer 7 in an isolation diffusion region is set to such level as no auto-doping increases the junction capacitance.
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