| CPC H01L 29/7788 (2013.01) [H01L 29/0607 (2013.01); H01L 29/66462 (2013.01); H01L 29/7787 (2013.01)] | 13 Claims |
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1. A vertical field effect transistor, comprising:
a drift region having a first conductivity type;
a trench structure on or above the drift region, the trench structure including at least one side wall at which a field effect transistor (FET) channel region is formed, the FET channel region including a III-V heterostructure for forming a two-dimensional electron gas at a boundary surface of the III-V heterostructure;
a shielding structure that is situated laterally adjacent to the at least one side wall of the trench structure and extends vertically into the drift region or vertically further in a direction of the drift region than the trench structure, the shielding structure having a second conductivity type that differs from the first conductivity type; and
a source/drain electrode that is electroconductively connected to the III-V heterostructure of the trench structure and to the shielding structure;
wherein the vertical field effect transistor includes at least one of the following four features (I)-(III):
(I) (i) the III-V heterostructure includes an AlGaN layer and a GaN layer that adjoins the AlGaN layer, (ii) the drift region is n-conductive, and (iii) the shielding structure includes at least one p-conductive GaN region whose dopant concentration is higher than a dopant concentration of the drift region;
(II) the shielding structure includes a laterally extending area that is situated in the drift region and extends laterally in a direction of the trench structure, and the vertical field effect transistor further includes at least one of the following two features (i)-(ii):
(i) the laterally extending area of the shielding structure situated in the drift region extends at least to below a portion of a base of the trench structure, and the vertical field effect transistor further includes at least one of the following two features (a)-(b):
(a) the laterally extending area is at least partially positioned directly under a lowest point of the trench structure; and
(b) the vertical field effect transistor further comprises an additional trench structure that is offset in a plane with respect to the trench structure, so that the source/drain electrode is situated between the trench structure and the additional trench structure, the shielding structure including an additional laterally extending area that is situated in the drift region and extends laterally at least to below a portion of a base of the additional trench structure; and
(ii) (a) the shielding structure further includes a vertically extending area that extends vertically between the source/drain electrode and the laterally extending area of the shielding structure, and (b) the laterally extending area and the vertically extending area are structured such that, in a cross-sectional view of the vertical field effect transistor, the laterally extending area and the vertically extending area form an ‘L’-shape composed of a vertical leg and a horizontal leg, the vertically extending area forming the vertical leg and extending vertically in a direction that is directed from a top side of the vertical field effect transistor towards the drift region, and the laterally extending area forming the vertical leg and extending laterally from the vertical leg in a direction that is directed from an exterior lateral side of the vertical field effect transistor radially inwards towards a lateral center of the vertical field effect transistor; and
(III) the vertical field effect transistor further comprises a region that (i) has the first conductivity type, (ii) is formed in the drift region at least below the trench structure, (iii) has a higher dopant concentration than the drift region, and (iv) adjoins the shielding structure.
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