Semiconductor device

1. A semiconductor device comprising:

a photodiode formed using a silicon substrate;

a wide-bandgap semiconductor layer disposed on said silicon substrate and having a bandgap larger than that of silicon; and

a switching element formed using said wide-bandgap semiconductor layer, wherein

said switching element is electrically connected to said photodiode to be on/off-controlled by a control signal from said photodiode, and

wherein said photodiode is covered with said wide-bandgap semiconductor layer.

2. The semiconductor device according to claim 1 , wherein

said photodiode has a cathode-side electrode and an anode-side electrode,

said switching element has a first electrode, a second electrode, and a control electrode,

said cathode-side electrode of said photodiode is electrically connected to said first electrode of said switching element, and

said anode-side electrode of said photodiode is electrically connected to said control electrode of said switching element.

3. The semiconductor device according to claim 1 , further comprising one or more additional photodiodes electrically connected in series between said photodiode and said switching element.

4. The semiconductor device according to claim 1 , further comprising an amplification circuit formed using said silicon substrate and amplifying and providing said control signal from said photodiode to said switching element.

5. The semiconductor device according to claim 4 , wherein

said photo diode has a cathode-side electrode and an anode-side electrode,

said switching element has a first electrode, a second electrode, and a control electrode, and

said amplification circuit is electrically connected so as to amplify voltage between said cathode-side electrode and said anode-side electrode of said photodiode and apply the amplified voltage between said first electrode and said control electrode of said switching element.

6. The semiconductor device according to claim 1 , wherein said wide-bandgap semiconductor layer includes at least any of a GaN layer, an Al GaN layer, an InGaN layer, and an InAlGaN layer.

7. The semiconductor device according to claim 1 , wherein a shield electrode arranged to surround a periphery of said photodiode and electrically connected to a ground electrode is provided on said wide-bandgap semiconductor layer in an upper region of said photodiode.

8. The semiconductor device according to claim 1 , wherein said switching element formed using said wide-bandgap semiconductor layer is an FET, a gate electrode of said FET is a Schottky gate, and said FET is a normally-off type.

9. A method of manufacturing a semiconductor device, said method comprising:

providing a photodiode formed using a silicon substrate;

providing a wide-bandgap semiconductor layer disposed on said silicon substrate and having a bandgap larger than that of silicon; and

providing a switching element formed using said wide-bandgap semiconductor layer, wherein said switching element is electrically connected to said photodiode to be on/off-controlled by a control signal from said photodiode, and wherein said photodiode is covered with said wide-bandgap semiconductor layer,

wherein

an impurity diffusion process is performed on said silicon substrate to form said light-receiving element, and

said wide-bandgap semiconductor layer is thereafter epitaxially grown on said silicon substrate.

10. The method of manufacturing the semiconductor device according to claim 9 , wherein

said silicon substrate includes a first kind of through groove and a second kind of through groove which penetrate the substrate,

said first kind of through groove is a groove for forming an electrode passing through said silicon substrate,

said second kind of through groove is a groove for forming an isolation region passing through said silicon substrate,

insulating films are formed at the same time on inner surfaces of said both kinds of through grooves,

said first kind of through groove has a width in which a space for forming an electrode is left even after formation of said insulating film, and

said second kind of through groove has a width that is filled with said insulating film.

11. A semiconductor device comprising:

at least one photodiode including diffusion regions provided in a first portion of a silicon substrate;

a wide-bandgap semiconductor layer disposed on said silicon substrate, the wide-band gap semiconductor layer having a bandgap larger than that of silicon; and

a switching element including said wide-bandgap semiconductor layer formed over a second portion of said silicon substrate, the switching element further including a control element responsive to a control signal provided from said at least one photodiode to provide on/off control of said switching element,

wherein said at least photodiode is covered with said wide-bandgap semiconductor layer.

12. The semiconductor device according to claim 11 , wherein

said at least one photodiode has a cathode-side electrode and an anode-side electrode,

said switching element has a first electrode, a second electrode, and a control electrode acting as said control element,

said cathode-side electrode of said at least one photodiode is electrically connected to said first electrode of said switching element, and

said anode-side electrode of said at least one photodiode is electrically connected to said control electrode of said switching element.

13. The semiconductor device according to claim 11 , further comprising one or more additional photodiodes electrically connected in series between said at least one photodiode and said control element of said switching element.

14. The semiconductor device according to claim 11 , further comprising an amplification circuit formed on said silicon substrate and amplifying and providing said control signal from said at least one photodiode to said control element of said switching element.

15. The semiconductor device according to claim 14 , wherein

said at least one photodiode has a cathode-side electrode and an anode-side electrode,

said switching element has a first electrode, a second electrode, and a control electrode acting as said control element, and

said amplification circuit is electrically connected so as to amplify voltage between said cathode-side electrode and said anode-side electrode of said photodiode and to apply the amplified voltage between said first electrode and said control electrode of said switching element.

16. The semiconductor device according to claim 11 , wherein said wide-bandgap semiconductor layer includes at least one of a GaN layer, an AlGaN layer, an InGaN layer, and an InAlGaN layer.

17. The semiconductor device according to claim 11 , further comprising a shield electrode arranged to surround a periphery of said at least one photodiode, said shield electrode being electrically connected to a ground electrode and being provided on said wide-bandgap semiconductor layer in an upper region of said at least one photodiode.

18. The semiconductor device according to claim 11 , wherein said switching element formed using said wide-bandgap semiconductor layer is an FET, a gate electrode of said FET is a Schottky gate and functions as said control element, and said FET is a normally-off type.