Trench DMOS power transistor with field-shaping body profile and three-dimensional geometry
DCFirst Claim
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1. A trench DMOS transistor cell comprising:
- a substrate of semiconductor material of heavily doped first electrical conductivity type;
a first covering layer of semiconductor material of said first electrical conductivity type lying on the substrate;
a second covering layer of semiconductor material of second electrical conductivity type lying on the first covering layer;
a third covering layer of semiconductor material of heavily doped said first electrical conductivity type and having a top surface and partly lying over the second covering layer, wherein a portion of the second covering layer is heavily doped and this portion extends both vertically upward and downward, an upward portion extending through the third covering layer to the top surface of the third covering layer and a downward portion extending downward into the first covering layer;
a trench having a bottom surface and side surfaces and extending vertically downward from the top surface of the third covering layer through the third covering layer and the second covering layer and through a portion of the first covering layer, wherein the bottom surface of the trench lies above a lowest part of the downward portion of the second covering layer;
electrically conducting semiconductor material positioned within the trench;
a layer of oxide positioned within the trench between the electrically conducting semiconductor material and the bottom and side surfaces of the trench; and
three electrodes electrically coupled to the electrically conducting semiconductor material, to the third covering layer and to the substrate, respectively.
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Abstract
Power MOSFET apparatus, and method for its production, that suppresses voltage breakdown near the gate, using a polygon-shaped trench in which the gate is positioned in order to suppress oxide dielectric breakdown, using a shaped deep body junction that partly lies below the trench bottom to force voltage breakdown away from the trench surfaces and into the bulk of the semiconductor material, and using special procedures for growth of gate oxide at various trench corners.
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Citations
14 Claims
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1. A trench DMOS transistor cell comprising:
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a substrate of semiconductor material of heavily doped first electrical conductivity type; a first covering layer of semiconductor material of said first electrical conductivity type lying on the substrate; a second covering layer of semiconductor material of second electrical conductivity type lying on the first covering layer; a third covering layer of semiconductor material of heavily doped said first electrical conductivity type and having a top surface and partly lying over the second covering layer, wherein a portion of the second covering layer is heavily doped and this portion extends both vertically upward and downward, an upward portion extending through the third covering layer to the top surface of the third covering layer and a downward portion extending downward into the first covering layer; a trench having a bottom surface and side surfaces and extending vertically downward from the top surface of the third covering layer through the third covering layer and the second covering layer and through a portion of the first covering layer, wherein the bottom surface of the trench lies above a lowest part of the downward portion of the second covering layer; electrically conducting semiconductor material positioned within the trench; a layer of oxide positioned within the trench between the electrically conducting semiconductor material and the bottom and side surfaces of the trench; and three electrodes electrically coupled to the electrically conducting semiconductor material, to the third covering layer and to the substrate, respectively.
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2. A trench DMOS transistor cell comprising:
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a substrate of semiconductor material of heavily doped first electrical conductivity type having a top surface; a first covering layer of semiconductor material of first electrical conductivity type having a top surface and being contiguous to and overlying the substrate top surface; a second covering layer of semiconductor material of second electrical conductivity type having a top surface and being contiguous to the top surface of the first covering layer and extending vertically downward from the top surface of the first covering layer into an upper portion of the first covering layer; a third covering layer of semiconductor material of heavily doped first electrical conductivity type having a top surface and being contiguous to and partly overlying the top surface of the second covering layer, wherein a portion of the second covering layer is heavily doped and this portion extends vertically upward through the third covering layer to the top surface of the third covering layer and forms an exposed pattern of the second covering layer adjacent in the top surface of the third covering layer, wherein the maximum depth of the heavily doped portion of the second covering layer relative to the top surface of the third covering layer is a predetermined number d1, and wherein the depth of the top surface of the substrate at a position that underlies the position of maximum depth of the heavily doped portion of the second covering layer is a second predetermined number d2 ; a trench having side surfaces and bottom surfaces and extending vertically downward from the top surface of the third covering layer through the third covering layer, through the second covering layer and through a portion of, but not all of, the first covering layer, the trench bottom surface having a maximum depth relative to the top surface of the third covering layer equal to a third predetermined number d3 where d3 <
d1, wherein the trench in horizontal cross section is approximately a polygonal stripe with stripe width approximately equal to a fourth predetermined number b, and wherein this polygonal stripe laterally surrounds and is spaced apart from the exposed pattern of the second covering layer at the top surface of the third covering layer;a layer of oxide, positioned within the trench and contiguous to the bottom surfaces and side surfaces of the trench so that a portion of, but not all of, the trench is filled with this oxide layer; electrically conducting semiconductor material, having resistivity of approximately one ohm-cm, that is contiguous to the oxide layer and positioned within the trench so that this electrically conducting semiconductor material is spaced apart from the side walls and the bottom walls of the trench by the oxide layer; and three electrodes that are electrically coupled to the electrically conducting semiconductor material in the trench, to the third covering layer and to the substrate, respectively. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification