Trench-gate field-effect transistors and their manufacture
First Claim
1. A trench-gate field-effect transistor comprising a semiconductor body into which an insulated gate electrode extends in a trench from a major surface of the body, successively through a drain region, a drain drift region, and a transistor body region to reach an underlying source region of the transistor, wherein the trench is lined with a gate dielectric that insulates the gate electrode from said drain, drain drift, body and source regions, the drain, drain drift and source regions are of a second conductivity type that is opposite to a first conductivity type of the body region, the drain region is adjacent to said major surface and has a higher doping concentration than the drain drift region, the gate dielectric is thicker adjacent to the drain region than adjacent to a channel-accommodating portion of the body region, the body region comprises an overlying layer that provides the channel-accommodating portion and that extends over a bottom portion of the body region that is more highly doped than the overlying layer, the highly doped bottom portion forms a leaky p-n junction with the underlying source region at an area that is separated laterally from the insulated gate electrode by an active portion of the source region, the active portion of the source region extends adjacent to the trench across the highly doped bottom portion of the body region to connect with the channel-accommodating portion of the body region, and the leaky p-n junction provides a buried electrical short that electrically shorts the body region to the underlying source region.
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Accused Products
Abstract
In a trench-gate field-effect transistor of inverted configuration, the drain region (14) is adjacent to the surface with the insulated trench-gate structure (11,12). The gate dielectric 12 is thicker adjacent to the drain region (14), and preferably also the drain drift region (14a), than it is adjacent to the channel-accommodating portion (15a) of the transistor body region (15). Another portion (15b) of the transistor body region (15) is electrically shorted to the underlying source region (13) by a buried electrical short (35). This buried short is provided by a leaky p-n junction (35) between a highly doped (p+) bottom portion (15b) of the body region and the underlying source region (13), at an area that is separated laterally from the insulated gate electrode (11) by an active portion (13a) of the source region adjacent to the gate trench (20). This portion (13a) of the source region can be formed by dopant implantation and/or diffusion via the lower portion of the trench (20). It extends across the highly doped bottom portion (15b) of the body region to connect with the channel-accommodating portion (15a) adjacent to the trench-gate structure (11,12). A compact layout of drain and trench-gate structures is achievable at the body surface (10a), and a compact layout of the buried electrical short (35) is achievable with the underlying source region (13).
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Citations
11 Claims
- 1. A trench-gate field-effect transistor comprising a semiconductor body into which an insulated gate electrode extends in a trench from a major surface of the body, successively through a drain region, a drain drift region, and a transistor body region to reach an underlying source region of the transistor, wherein the trench is lined with a gate dielectric that insulates the gate electrode from said drain, drain drift, body and source regions, the drain, drain drift and source regions are of a second conductivity type that is opposite to a first conductivity type of the body region, the drain region is adjacent to said major surface and has a higher doping concentration than the drain drift region, the gate dielectric is thicker adjacent to the drain region than adjacent to a channel-accommodating portion of the body region, the body region comprises an overlying layer that provides the channel-accommodating portion and that extends over a bottom portion of the body region that is more highly doped than the overlying layer, the highly doped bottom portion forms a leaky p-n junction with the underlying source region at an area that is separated laterally from the insulated gate electrode by an active portion of the source region, the active portion of the source region extends adjacent to the trench across the highly doped bottom portion of the body region to connect with the channel-accommodating portion of the body region, and the leaky p-n junction provides a buried electrical short that electrically shorts the body region to the underlying source region.
- 9. A method of manufacturing a, trench-gate field-effect transistor having a semiconductor body into which an insulated gate electrode extends in a trench from a major surface of the body, successively through a drain region, a drain drift region, and a transistor body region to reach an underlying source region of the transistor, wherein the trench is lined with a gate dielectric that insulates the gate electrode from said drain, drain drift, body and source regions, the drain, drain drift and source regions are of a second conductivity type that is opposite to a first conductivity type of the body region, the drain region is adjacent to said major surface and has a higher doping concentration than the drain drift region, the gate dielectric is thicker adjacent to the drain region than adjacent to a channel-accommodating portion of the body region, the body region comprises an overlying layer that provides the channel-accommodating portion and that extends over a bottom portion of the body region that is more highly doped than the overlying layer, the highly doped bottom portion forms a leaky p-n junction with the underlying source region at an area that is separated laterally from the insulated gate electrode by an active portion of the source region, the active portion of the source region extends adjacent to the trench across the highly doped bottom portion of the body region to connect with the channel-accommodating portion of the body region, and the leaky p-n junction provides a buried electrical short that electrically shorts the body region to the underlying source region, including the steps of growing on a monocrystalline substrate stacked epitaxial layers for providing the highly doped bottom portion of the body region, the channel-accommodating portion of the body region, the drain drift region and the drain region, and thereafter etching a trench for the insulated gate electrode successively through the drain region, the drain drift region, and the transistor body region to reach the underlying source region.
Specification