Trenched semiconductor devices and their manufacture

• US 6,956,264 B2
• Filed: 12/03/2002
• Issued: 10/18/2005
• Est. Priority Date: 12/08/2001
• Status: Expired due to Fees

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Hijzen, Erwin A., Hueting, Raymond J. E., In't Zandt, Michael A. A.
• Primary Examiner(s): Kang, Donghee
• Application Number:
  US10/308,656
• Publication Number:
  US 20030146470A1
• Time in Patent Office: 1,050 Days
• Field of Search: 438/294, 438/296, 257/330, 257/331, 257/332, 257/341, 257/342
• US Class Current: 257/330
• CPC Class Codes: H01L 21/28211 in a gaseous ambient using an oxygen or a water vapour, e.g. RTO, possibly through a layer H01L21/28194 and H01L21/28202 take precedence
• CPC Class Codes: H01L 29/4232 with insulated gate
• CPC Class Codes: H01L 29/42368 the thickness being non-uniform
• CPC Class Codes: H01L 29/4238 characterised by the surface lay-out
• CPC Class Codes: H01L 29/51 Insulating materials associated therewith for MIS structures on thin film semiconductor H01L29/4908
• CPC Class Codes: H01L 29/511 with a compositional variation, e.g. multilayer structures H01L29/516 takes precedence
• 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

Abstract

In semiconductor devices which include an insulated trench electrode (11) in a trench (20), for example, trench-gate field effect power transistors and trenched Schottky diodes, a cavity (23) is provided between the bottom (25) of the trench electrode (11) and the bottom (27) of the trench (20) to reduce the dielectric coupling between the trench electrode (11) and the body portion at the bottom (27) of the trench in a compact manner. In power transistors, the reduction in dielectric coupling reduces switching power losses, and in Schottky diodes, it enables the trench width to be reduced.

Claims

1. A semiconductor device including an insulated trench electrode in a trench, the trench extending in a semiconductor body portion of the device, wherein the trench electrode is dielectrically coupled to the body portion by an insulating layer at a side-wall of the trench, and there is a cavity located adjacent only a lower portion of the trench electrode and having a gaseous content between the bottom of the trench electrode and the bottom of the trench to provide a structure for reducing the dielectric coupling between the trench electrode and the body portion at the bottom of the trench.

2. A device of claim 1 wherein a passivation layer over at least one of the trench wall and the bottom of the trench electrode forms at least part of the wall of the cavity.

3. A device of claim 1 wherein the cavity extends along the sides of a lower portion of the trench electrode.

4. A device of claim 1 including a source region and a drain region of a first conductivity type, having therebetween a channel-accommodating region of an opposite, second conductivity type, wherein the trench electrode forms a gate and extends from the source region, through the channel-accommodating region to the drain region.

5. A device of claim 4 wherein the drain region comprises a drain drift region and a drain contact region, with the drain drift region between the channel-accommodating region and the drain contact region, and the drain drift region is doped to a lesser degree than the drain contact region, at least a portion of the cavity being between the trench electrode and the drain contact region.

6. A device of claim 5 wherein the cavity extends substantially from the trench electrode across the drain drift region towards the drain contact region.

7. A device of claim 1 wherein the body portion is a drift region contacted by a Schottky electrode which forms a Schottky barrier with the drift region.