Schottky barrier diode and MOSFET semiconductor device

• US 8,552,476 B2
• Filed: 09/19/2011
• Issued: 10/08/2013
• 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
• Primary Examiner(s): Maldonado, Julio J
• Assistant Examiner(s): ESKRIDGE, CORY W
• Application Number:
  US13/236,588
• Publication Number:
  US 20120241853A1
• Time in Patent Office: 750 Days
• Field of Search: 257/260, 257/263, 257/267, 257/256, 257/280, 257/288, 257/471, 257/476, 257/E29.002, 257/E29.013, 257/E29.148
• US Class Current: 257/267
• 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 on each inner wall of the first trenches;

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

a first semiconductor diffusion layer of the first conductivity type 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, and

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 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.

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

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

5. The semiconductor device according to claim 1, wherein

each of the insulation layers comprises:

a first insulation layer formed on an inner wall of one of the first trenches in a lower layer below the second position, and

a second insulation layer formed on the inner wall of one of the first trenches in an upper layer above the second position;

each of the conductive layers comprises;

a first conductive layer formed in one of the first trenches on the first insulation layer in the lower layer below the second position and extending downward from the second position to the first position, and

a second conductive layer formed in one of the first trenches on the second insulation layer in the upper layer above the second position and reaching the second position from the upper surface of the semiconductor layer; and

the first conductive layer is electrically connected to the anode electrode.