SEMICONDUCTOR DEVICE

• US 20120241853A1
• Filed: 09/19/2011
• Published: 09/27/2012
• Est. Priority Date: 03/25/2011
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: OHTA, Tsuyoshi, Arai, Masatoshi, Suzuki, Miwako
• Granted Patent: US 8,552,476 B2
• Time in Patent Office: Days
• US Class Current: 257/331
• CPC Class Codes: H01L 29/0619 with a supplementary region doped oppositely to or in rectifying contact with the semiconductor containing or contacting region, e.g. guard rings with PN or Schottky junction
• CPC Class Codes: H01L 29/407 Recessed field plates, e.g. trench field plates, buried field plates
• CPC Class Codes: H01L 29/41 characterised by their shape, relative sizes or dispositions
• CPC Class Codes: H01L 29/42368 the thickness being non-uniform
• CPC Class Codes: H01L 29/456 on silicon
• CPC Class Codes: H01L 29/47 Schottky barrier electrodes H01L29/435 takes precedence
• CPC Class Codes: H01L 29/66143 Schottky diodes
• CPC Class Codes: H01L 29/7806 the other device being a Schottky barrier diode
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236
• CPC Class Codes: H01L 29/872 Schottky diodes
• CPC Class Codes: H01L 29/8725 of the trench MOS barrier type [TMBS]

Abstract

A semiconductor layer has a second impurity concentration. First trenches are formed in the semiconductor layer to extend downward from an upper surface of the semiconductor layer. Each of insulation layers is formed along each of the inner walls of the first trenches. Each of conductive layers is formed to bury each of the first trenches via each of the insulation layers, and extends downward from the upper surface of the semiconductor layer to a first position. A first semiconductor diffusion layer reaches a second position from the upper surface of the semiconductor layer, is positioned between the first trenches, and has a third impurity concentration lower than the second impurity concentration. A length from the upper surface of the semiconductor layer to the second position is equal to or less than half a length from the upper surface of the semiconductor layer to the first position.

Claims

1. A semiconductor device comprising:

a cathode electrode;

a semiconductor substrate of a first conductivity type electrically connected to the cathode electrode and having a first impurity concentration;

a semiconductor layer of the first conductivity type formed on the semiconductor substrate and having a second impurity concentration lower than the first impurity concentration;

a plurality of first trenches formed in the semiconductor layer to extend downward from an upper surface of the semiconductor layer;

a plurality of insulation layers each formed along each of inner walls of the first trenches;

a plurality of conductive layers each formed to bury each of the first trenches via each of the insulation layers and extending downward from the upper surface of the semiconductor layer to a first position;

a first semiconductor diffusion layer reaching a second position from the upper surface of the semiconductor layer, positioned between the first trenches, and having a third impurity concentration lower than the second impurity concentration; and

an anode electrode formed on upper surfaces of the first semiconductor diffusion layer and the conductive layers, and having a schottky junction with the first semiconductor diffusion layer,

a length from the upper surface of the semiconductor layer to the second position being equal to or less than half a length from the upper surface of the semiconductor layer to the first position.

2. The semiconductor device according to claim 1, further comprising a plurality of second semiconductor diffusion layers of a second conductivity type provided between the insulation layers and the first semiconductor diffusion layer.

3. The semiconductor device according to claim 1, wherein the insulation layers include boron silicate glass.

4. The semiconductor device according to claim 2, wherein the second semiconductor diffusion layers are provided between the insulation layers and the semiconductor layer.

5. The semiconductor device according to claim 1, further comprising:

a second trench formed in the semiconductor layer to extend downward from the upper surface of the semiconductor layer;

a gate insulation film formed in an inner wall of the second trench; and

a gate electrode of MOSFET formed to bury the second trench via the gate insulation film.

6. The semiconductor device according to claim 1, wherein the cathode electrode includes titanium, nickel and gold.

7. The semiconductor device according to claim 1, wherein the anode electrode includes vanadium and aluminum.

8. A semiconductor device comprising:

a cathode electrode;

a semiconductor substrate of a first conductivity type electrically connected to the cathode electrode and having a first impurity concentration;

a semiconductor layer of the first conductivity type formed on the semiconductor substrate and having a second impurity concentration lower than the first impurity concentration;

a plurality of first trenches formed in the semiconductor layer to extend downward from an upper surface of the semiconductor layer;

a plurality of first insulation layers each formed along each of inner walls of the first trenches in a lower layer below a first position;

a plurality of first conductive layers each formed to bury each of the first trenches via each of the first insulation layers in the lower layer below the first position and extending downward from the first position to a second position;

a plurality of second insulation layers each formed along each of the inner walls of the first trenches in an upper layer above the first position;

a plurality of second conductive layers each formed to bury each of the first trenches via each of the second insulation layers in the upper layer above the first position and reaching the first position from the upper surface of the semiconductor layer;

a first semiconductor diffusion layer reaching a third position from the upper surface of the semiconductor layer, positioned between the first trenches, and having a third impurity concentration lower than the second impurity concentration; and

an anode electrode formed on upper surfaces of the first semiconductor diffusion layer and the second conductive layers, and having a schottky junction with the first semiconductor diffusion layer,

the first conductive layers being electrically connected to the anode electrode, and

a length from the upper surface of the semiconductor layer to the third position being equal to or less than half a length from the upper surface of the semiconductor layer to the second position.

9. The semiconductor device according to claim 8, further comprising a plurality of second semiconductor diffusion layers of a second conductivity type provided between the second insulation layers and the first semiconductor diffusion layer.

10. The semiconductor device according to claim 8, wherein a diameter of upper ends of the first trenches is greater than a diameter of lower ends of the first trenches.

11. The semiconductor device according to claim 8, wherein each of the first conductive layer comprises:

a tapered portion formed in a tapered shape in which a diameter becomes narrow from an upper end to a lower end; and

a columnar portion extending downward from the lower end of the tapered portion and formed in a columnar shape having the same diameter from an upper end to a lower end.

12. The semiconductor device according to claim 8, further comprising:

a second trench formed in the semiconductor layer to extend downward from the upper surface of the semiconductor layer;

a gate insulation film formed in an inner wall of the second trench; and

a gate electrode of MOSFET formed to bury the second trench via the gate insulation film.

13. The semiconductor device according to claim 8, wherein the cathode electrode includes titanium, nickel and gold.

14. The semiconductor device according to claim 8, wherein the anode electrode includes vanadium and aluminum.

15. A semiconductor device comprising:

a cathode electrode;

a semiconductor substrate of a first conductivity type electrically connected to the cathode electrode and having a first impurity concentration;

a first semiconductor layer of the first conductivity type formed on the semiconductor substrate and having a second impurity concentration lower than the first impurity concentration;

a plurality of first trenches formed in the first semiconductor layer to extend downward from an upper surface of the first semiconductor layer;

a plurality of insulation layers each formed along each of inner walls of the first trenches in a lower layer below a first position;

a plurality of conductive layers each formed to bury each of the first trenches via each of the insulation layers in a lower layer below the first position and extending downward from the first position to a second position;

a plurality of second semiconductor layers each formed to bury each of the first trenches in an upper layer above the first position;

a first semiconductor diffusion layer reaching a third position from the upper surface of the first semiconductor layer, positioned between the plurality of first trenches, and having a third impurity concentration lower than the second impurity concentration; and

an anode electrode formed on upper surfaces of the first semiconductor diffusion layer and the conductive layers, and having a schottky junction with the first semiconductor diffusion layer,

the conductive layers being electrically connected to the anode electrode, and

a length from the upper surface of the first semiconductor layer to the third position being equal to or less than half a length from the upper surface of the first semiconductor layer to the second position.

16. The semiconductor device according to claim 15, further comprising a plurality of second semiconductor diffusion layers of a second conductivity type provided between the second semiconductor layers and the first semiconductor diffusion layer.

17. The semiconductor device according to claim 15, wherein the second semiconductor layers include polysilicon containing boron silicate glass or polysilicon containing boron.

18. The semiconductor device according to claim 15, further comprising:

a second trench formed in the semiconductor layer to extend downward from the upper surface of the semiconductor layer;

a gate insulation film formed in an inner wall of the second trench; and

a gate electrode of MOSFET formed to bury the second trench via the gate insulation film.

19. The semiconductor device according to claim 15, wherein the cathode electrode includes titanium, nickel and gold.

20. The semiconductor device according to claim 15, wherein the anode electrode includes vanadium and aluminum.