VERTICAL POWER MOS-GATED DEVICE WITH HIGH DOPANT CONCENTRATION N-WELL BELOW P-WELL AND WITH FLOATING P-ISLANDS
First Claim
1. A vertical transistor comprising a semiconductor substrate having a first electrode on its bottom surface;
- a first layer of a first conductivity type overlying the substrate, the first layer having a first dopant concentration;
a first region of the first conductivity type overlying the first layer, the first region layer having a second dopant concentration higher than the first dopant concentration, the first region having a top surface;
a trench having a vertical sidewall adjoining the first region , the trench containing a conductor insulated from the first layer and first region;
a second region of a second conductivity type overlying the top surface of the first region, the second region having a top surface;
a third region of the first conductivity type overlying the top surface of the second region, wherein an area between the third region and an edge of the second region comprises a channel for inversion by a gate;
a conductive gate insulated from and proximate to the channel for creating a conductive path in the channel when the gate is biased above a threshold voltage, the gate also being insulated from and proximate to the first region for increasing a carrier concentration in the first region along a vertical section of the first region when the gate is biased to turn the transistor on so as to form a vertical low-conductivity path through the first region; and
a second electrode electrically contacting the second region and the third region, wherein when a voltage is applied between the first electrode and the second electrode and the gate is biased above the threshold voltage, a current flows between the first electrode and the second electrode.
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Accused Products
Abstract
In one embodiment, a power MOSFET or IGBT cell includes an N-type drift region grown over the substrate. An N-type layer, having a higher dopant concentration than the drift region, is then formed over the drift region. A P-well is formed over the N-type layer, and an N+ source/emitter region is formed in the P-well. A gate is formed over the P-well'"'"'s lateral channel and has a vertical extension into a trench. A positive gate voltage inverts the lateral channel and increases the vertical conduction in the N-type layer along the sidewalls of the trench to reduce on-resistance. A vertical shield field plate is also in the trench and may be connected to the gate. The field plate laterally depletes the N-type layer when the device is off to increase the breakdown voltage. Floating P-islands in the N-type drift region increase breakdown voltage and reduce the saturation current.
22 Citations
20 Claims
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1. A vertical transistor comprising a semiconductor substrate having a first electrode on its bottom surface;
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a first layer of a first conductivity type overlying the substrate, the first layer having a first dopant concentration; a first region of the first conductivity type overlying the first layer, the first region layer having a second dopant concentration higher than the first dopant concentration, the first region having a top surface; a trench having a vertical sidewall adjoining the first region , the trench containing a conductor insulated from the first layer and first region; a second region of a second conductivity type overlying the top surface of the first region, the second region having a top surface; a third region of the first conductivity type overlying the top surface of the second region, wherein an area between the third region and an edge of the second region comprises a channel for inversion by a gate; a conductive gate insulated from and proximate to the channel for creating a conductive path in the channel when the gate is biased above a threshold voltage, the gate also being insulated from and proximate to the first region for increasing a carrier concentration in the first region along a vertical section of the first region when the gate is biased to turn the transistor on so as to form a vertical low-conductivity path through the first region; and a second electrode electrically contacting the second region and the third region, wherein when a voltage is applied between the first electrode and the second electrode and the gate is biased above the threshold voltage, a current flows between the first electrode and the second electrode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A vertical transistor comprising
a semiconductor substrate having a first electrode on its bottom surface; -
a first layer of a first conductivity type overlying the substrate; a trench having a vertical sidewall, the trench containing a conductor insulated from the first layer; a first region of a second conductivity type overlying the first layer, the first region having a top surface; a second region of the first conductivity type overlying the top surface of the first region, wherein an area between the second region and an edge of the first region comprises a channel for inversion by a gate; a conductive gate insulated from and proximate to the channel for creating a conductive path in the channel when the gate is biased above a threshold voltage; at least one third region of the second conductivity type formed completely within the first layer, the at least one third region electrically floating; and a second electrode electrically contacting the first region and the second region, wherein when a voltage is applied between the first electrode and the second electrode and the gate is biased above the threshold voltage, a current flows between the first electrode and the second electrode. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification