| 主权项 |
1. A bi-directional trench field effect power transistor, comprising:
a substrate with a substrate top surface; a layer stack extending over the substrate top surface, a first vertical trench and a second vertical trench being present in the layer stack, each of said first and second vertical trenches extending in a vertical direction from a top layer of the layer stack towards the substrate; a first current terminal and a second current terminal, the first current terminal being situated in said vertical direction below the second current terminal and the second current terminal being situated on or above the top layer; and an electrical path which can be selectively enabled or disabled to allow current to flow in a first direction or a second direction, opposite to the first direction, between the first current terminal and the second current terminal, the electrical path comprising:
a body extending laterally between the first and second vertical trenches and vertically between said first current terminal and said second current terminal;a first drift region extending, in said vertical direction, between the body and the first current terminal;a second drift region extending, in said vertical direction, between the body and the second current terminal; wherein the first vertical trench and the second vertical trench have the same of option (a) and/or (b); option (a) being:
the first and second vertical trenches extend, in said vertical direction, from said top layer beyond an upper boundary of the first drift region, and in a lateral direction parallel to the substrate top-surface electrically isolate, and define, the first drift region; option (b) being: each of said first and second vertical trenches comprising:
a gate electrode in an first part of the vertical trench, the gate electrode being electrically coupled to the body, for forming, when a suitable voltage is applied to the gate, a vertical channel in the body through which a current can flow from the first drift region to the second drift region or vice versa;a lower shield plate, the shield plate being situated in a lower part of the trench, the lower part being closer to the substrate than the first part, for generating an accumulation layer in the first drift region when the lower shield plate is biased with respect to the first current terminal in a first polarity and locally reducing the electrical field density when the lower shield plate is biased with respect to the first current terminal in a second polarity; anda body-side vertical sidewall, and another vertical sidewall facing the body-side vertical sidewall, of which at least the body-side vertical sidewall is covered with a dielectric which separates the gate electrode and the shield plate from the body-side vertical sidewall, the dielectric being thicker in the first part than in the lower part. |
