Abstract: A feedback resistor of a feedback circuit included in a photo-receiving amplifier element is formed on an island region in which an electric potential is in a floating state. The island region is electrically isolated from an island region on which an element other than the feedback resistor is formed. This enables the response speed of the photo-receiving amplifier element to be increased without changing the process of the circuit or varying a resistance value of the feedback resistor in a first-stage amplifier unit.

Abstract: A feedback resistor of a feedback circuit included in a photo-receiving amplifier element is formed on an island region in which an electric potential is in a floating state. The island region is electrically isolated from an island region on which an element other than the feedback resistor is formed. This enables the response speed of the photo-receiving amplifier element to be increased without changing the process of the circuit or varying a resistance value of the feedback resistor in a first-stage amplifier unit.

Abstract: Si.sub.3 N.sub.4 having high humidity resistance is used as a surface protecting insulating film covering a metal layer. At a bonding pad portion where metal layer is directly exposed, coverage is provided by anti-corrosion metal portion consisting of a titanium-tungsten alloy layer and gold layers. At a signal processing circuit portion, light intercepting structure and interconnection are provided similarly by titanium-tungsten alloy layer and gold layer. Thus humidity resistance of a photodetector element containing a circuit element is improved, and the gold layer allows direct die-bonding of a laser chip or the like. Further, since light intercepting structure and interconnection can be provided at the signal processing circuit portion simultaneously with the formation of gold layer for the bonding pad portion, the number of manufacturing steps can be reduced.

Abstract: A waveguide-photodetector includes a semiconductor substrate; a waveguide section, provided on the semiconductor substrate, for propagating light; an opto-electric converting section, provided in the semiconductor substrate, for converting the light into an electric signal; and an insulative layer provided between the semiconductor substrate and the waveguide section. The waveguide section includes at least an introducing part for introducing the light to the waveguide section, a coupling part for coupling the light introduced to the waveguide section to the opto-electric converting section, and a propagating part for propagating the light from the introducing part to the coupling part. The insulative layer includes a first region for defining a position and a shape of an impurity diffused region of the opto-electric converting section, a second region which encloses the first region and is thicker than the first region, and a step portion between the first region and the second region.

Abstract: A light receiving device including a semiconductor substrate of a first conductivity type; a first semiconductor layer of a second conductivity type which is formed on the semiconductor substrate of the first conductivity type; and a semiconductor layer of the first conductivity type which elongates from a surface of the first semiconductor substrate of the second conductivity type to reach a surface of the semiconductor substrate of the first conductivity type, the semiconductor layer splitting the first semiconductor layer of the second conductivity type into a plurality of semiconductor regions of the second conductivity type. The portion of the semiconductor layer of the first conductivity type which overlaps with the semiconductor substrate of the first conductivity type is formed as a semiconductor region of the first conductivity type and has a high-impurity density.

Abstract: A light-receiving semiconductor device with improved light sensitivity. On a semiconductor substrate of a first conductivity type is formed a plurality of buried layers of a second conductivity type divided by a narrow dividing region. A surface semiconductor layer of the first conductivity type covers the buried layers and the substrate. A connecting semiconductor region of the second conductivity type extends from each of the plurality of the buried layers to the surface of the surface semiconductor layer. An anti-light-reflecting film formed on the surface of the surface semiconductor layer covers a region above the dividing region as well as above the plurality of buried layers. Each of the plurality of buried layers forms a light responsive element with the substrate.