Floating-shield triple-gate MOSFET
First Claim
1. A trench MOSFET comprising:
- a semiconductor die including a substrate, an active device region formed upon the substrate, and an interconnection region formed upon the active device region, the active device region and the interconnection region separated by an interface surface;
a pair of trenches formed in the active device region, each of the trenches extending from the interface surface to a dielectric trench bottom, the pair of trenches laterally separated from one another by an intervening semiconductor pillar;
a conductive gate located within each of the trenches and separated from the intervening semiconductor pillar by a gate dielectric;
a first conductive field plate located within each of the trenches, the first conductive field plate electrically connected to a biasing circuit net in the interconnection region, the first conductive field plate extending to a first depth location below the conductive gate, the first conductive field plate laterally separated from the intervening semiconductor pillar by a dielectric trench sidewall;
a second conductive field plate located within each of the trenches, the second conductive field plate extending to a second depth location below the first conductive field plate and separated from the first conductive field plate by an intervening dielectric layer, the second conductive field plate floated but capacitively coupled via the intervening dielectric layer to the first conductive field plate, the second conductive field plate laterally separated from the intervening semiconductor pillar by the dielectric trench sidewall;
a source region in the intervening semiconductor pillar, the source region abutting each of the trenches;
a body region in the intervening semiconductor pillar, the body region abutting each of the trenches; and
a drain region in the intervening semiconductor pillar contiguously extending from the body region to the substrate, wherein the drain region has a dopant concentration that varies from a drain/body interface to the substrate,wherein configuration of the first and second conductive field plates, the intervening dielectric layer, the dielectric trench sidewall, and the dopant concentration in the drain region causes, under predetermined maximum bias conditions, first and second local maxima of the electric field in the drain region located proximate the drain/body interface and the dielectric trench bottom, respectively, to be substantially equal in magnitude.
1 Assignment
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Accused Products
Abstract
Apparatus and associate methods relate to a high-voltage MOSFET bounded by two trenches, each having dielectric sidewalls and a dielectric bottom isolating a top field plate and a bottom field plate. The top field plate is electrically connected to a biasing circuit net, and the bottom field plate is biased via a capacitive coupling to the top field plate. The upper field plate and lower field plate are configured to deplete the majority carriers in a drain region of the MOSFET bounded by the two trenches so as to equalize two local maxima of an electric field induced by a drain/body bias, the two local maxima located proximate a drain/body metallurgical junction and proximate a trench bottom. The two local maxima of the electric field are equalized by controlling a depth location of an intervening dielectric between the upper field plate and the lower field plate.
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Citations
13 Claims
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1. A trench MOSFET comprising:
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a semiconductor die including a substrate, an active device region formed upon the substrate, and an interconnection region formed upon the active device region, the active device region and the interconnection region separated by an interface surface; a pair of trenches formed in the active device region, each of the trenches extending from the interface surface to a dielectric trench bottom, the pair of trenches laterally separated from one another by an intervening semiconductor pillar; a conductive gate located within each of the trenches and separated from the intervening semiconductor pillar by a gate dielectric; a first conductive field plate located within each of the trenches, the first conductive field plate electrically connected to a biasing circuit net in the interconnection region, the first conductive field plate extending to a first depth location below the conductive gate, the first conductive field plate laterally separated from the intervening semiconductor pillar by a dielectric trench sidewall; a second conductive field plate located within each of the trenches, the second conductive field plate extending to a second depth location below the first conductive field plate and separated from the first conductive field plate by an intervening dielectric layer, the second conductive field plate floated but capacitively coupled via the intervening dielectric layer to the first conductive field plate, the second conductive field plate laterally separated from the intervening semiconductor pillar by the dielectric trench sidewall; a source region in the intervening semiconductor pillar, the source region abutting each of the trenches; a body region in the intervening semiconductor pillar, the body region abutting each of the trenches; and a drain region in the intervening semiconductor pillar contiguously extending from the body region to the substrate, wherein the drain region has a dopant concentration that varies from a drain/body interface to the substrate, wherein configuration of the first and second conductive field plates, the intervening dielectric layer, the dielectric trench sidewall, and the dopant concentration in the drain region causes, under predetermined maximum bias conditions, first and second local maxima of the electric field in the drain region located proximate the drain/body interface and the dielectric trench bottom, respectively, to be substantially equal in magnitude. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A trench MOSFET comprising:
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a semiconductor die having a lower substrate region, an intermediate active region, and an upper interconnection region, the intermediate active region having a top interface surface delineating a plane separating the intermediate active region from the upper interconnection region, wherein the intermediate active region is formed of alternating series of semiconductor pillars and longitudinal trenches, wherein each of the semiconductor pillars has a source region, a body region, and a drain region contiguously extending form the body region to the lower substrate region, wherein the drain region has a dopant concentration that varies from a drain/body interface to the lower substrate region, and wherein each of the longitudinal trenches vertically extends from the top interface surface to a dielectric trench bottom, each of the longitudinal trenches having conductive gates on either of two lateral ends, the conductive gates separated from the body regions of adjacent semiconductor pillars by a gate dielectric, each of the longitudinal trenches having an upper conductive field plate and a lower conductive field plate, the upper and lower conductive field plates separated from the drain regions of adjacent semiconductor pillars by dielectric sidewalls, the upper and lower conductive field plates in each of the longitudinal trenches vertically aligned to one another, the upper conductive field plate being biased by electrical conduction with a circuit net in the upper interconnection region, the lower conductive field plate floated and capacitively coupled via an intervening dielectric layer to the upper conductive field plate, wherein configuration of the upper and lower conductive field plates, the intervening dielectric layer, the dielectric sidewall, and the dopant concentration in the drain region causes, under predetermined maximum bias conditions, first and second local maxima of the electric field in the drain region located proximate the drain/body interface and the dielectric trench bottom, respectively, to be substantially equal in magnitude. - View Dependent Claims (11, 12, 13)
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Specification