| CPC H01L 29/7788 (2013.01) [H01L 29/2003 (2013.01); H01L 29/205 (2013.01); H01L 29/207 (2013.01)] | 15 Claims |

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1. A heterojunction semiconductor device with low on-resistance comprising:
a metal drain electrode, a substrate disposed on the metal drain electrode, a buffer layer disposed on the substrate, a current blocking layer disposed within the buffer layer, a gate structure disposed on the buffer layer and comprising a metal gate electrode, a metal source electrode disposed above the metal gate electrode, a first passivation layer disposed between the metal gate electrode and the metal source electrode, and a second passivation layer disposed between the metal gate electrode and the buffer layer;
wherein the current blocking layer comprises a first-level current blocking layer, a second-level current blocking layer, and a third-level current blocking layer which are sequentially arranged from top to bottom, the first-level current blocking layer is continuous as one whole piece and has only one inner opening when viewed in plan-view, the second-level current blocking layer is continuous as one whole piece and has only one inner opening when viewed in plan-view, and the third-level current blocking layer is continuous as one whole piece and has only one inner opening when viewed in plan-view, and symmetry centers of the first-level current blocking layer, the second-level current blocking layer, and the third-level current blocking layer are collinear;
the inner opening of the first-level current blocking layer is larger than the inner opening of the second-level current blocking layer, and the inner opening of the second-level current blocking layer is larger than the inner opening of the third-level current blocking layer, presenting a trend of becoming smaller level by level.
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