Semiconductor device and method of manufacturing thereof

• US 6,979,874 B2
• Filed: 10/30/2002
• Issued: 12/27/2005
• Est. Priority Date: 06/18/1997
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Harada, Masana
• Primary Examiner(s): Nadav, Ori
• Application Number:
  US10/283,132
• Publication Number:
  US 20030057482A1
• Time in Patent Office: 1,154 Days
• Field of Search: 257155-156, 257267-269, 257/260, 257471-486, 257/622, 257/656, 257280-284, 257440-457, 438570-571, 438576-577, 438/581, 438/92
• US Class Current: 257/475
• 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 29/66136 PN junction diodes
• CPC Class Codes: H01L 29/66356 Gated diodes, e.g. field controlled diodes [FCD], static induction thyristors [SITh], field controlled thyristors [FCTh]
• CPC Class Codes: H01L 29/861 Diodes
• CPC Class Codes: H01L 29/872 Schottky diodes

Abstract

A plurality of p anode regions are formed at one surface of an n⁻ substrate. A trench is formed in each p anode region. An ohmic junction region is formed between an anode metallic electrode and the p anode region. The p anode region has a minimum impurity concentration at a portion near the ohmic junction region which enables ohmic contact. A cathode metallic electrode is formed at the other surface of the n⁻ substrate with an n⁺ cathode region interposed. Accordingly, a semiconductor device which has an improved withstand voltage and in which the reverse recovery current is reduced can be obtained.

Claims

1. A semiconductor device comprising:

a semiconductor substrate of a first conductivity type;

a plurality of trench portions selectively formed at a first main surface of said semiconductor substrate;

a conductor embedded in each said trench portion with a first insulating layer there between;

a plurality of impurity regions of a second conductivity type which is formed at a region between said trench portions and at said first main surface of said semiconductor substrate, in contact with at least one of opposite sides of adjacent trench portions and located shallower than said trench portion; and

a first electrode layer formed on said first main surface of said semiconductor substrate, wherein;

said first electrode layer and each said impurity region form an ohmic contact at said first main surface;

each said impurity region has a minimum impurity concentration at a portion near said first main surface which enables ohmic contact with said first electrode layer, and has an impurity concentration still lower than said minimum impurity concentration which enables ohmic contact at a portion at said first main surface other than the portion near said first main surface;

each said impurity region of the second conductivity type is in contact with at least the edge along the opening of the trench portion and the side, adjacent to the edge, of the trench portion, and each said impurity region of the second conductivity type is in direct contact with the semiconductor substrate of the first conductivity type; and

each said impurity region is formed to be in contact with opposite sides of said trench portions adjacent to each other, and said first electrode layer and a region of the first conductivity type of said semiconductor substrate form a Schottky junction at said first main surface.

2. The semiconductor device according to claim 1, wherein

said first electrode layer is formed of aluminum, and

said minimum impurity concentration which enables ohmic contact with said first electrode layer is 1×

10¹⁶–

1×

10¹⁷/cm³.

3. The semiconductor device according to claim 1, wherein

each said impurity region is formed at both sides of each said trench portion to be in contact with one side of each said trench portion, and

said first electrode layer and a region of the first conductivity type of said semiconductor substrate form a Schottky junction at said first main surface.

4. The semiconductor device according to claim 3, further comprising:

a second insulating layer formed on each said conductor and electrically insulates said first electrode layer from each said conductor; and

an electrode portion electrically connected with each said conductor.

5. The semiconductor device according to claim 3, wherein

said first electrode layer is formed of aluminum, and said minimum impurity concentration which enables ohmic contact with said first electrode layer is 1×

10¹⁶–

1×

10¹⁷/cm³.

6. The semiconductor device according to claim 1, wherein

said impurity region is formed to be in contact with opposite sides of said trench portions adjacent to each other, and further comprising:

a second insulating layer formed on each said conductor and electrically insulates said first electrode layer from each said conductor; and

an electrode portion electrically connected with each said conductor.

7. The semiconductor device according to claim 6, wherein

said first electrode layer is formed of aluminum, and said minimum impurity concentration which enables ohmic contact with said first electrode layer is 1×

10¹⁶–

1×

10¹⁷/cm³.

8. The semiconductor device according to claim 1, wherein

said first electrode layer is formed of aluminum, and said minimum impurity concentration which enables ohmic contact with said first electrode layer is 1×

10¹⁶–

1×

10¹⁷/cm³.