Stepped trench MOSFET and method of fabricating the same

摘要

A step trench metal-oxide-semiconductor field-effect transistor comprises a drift layer, a first semiconductor region, a stepped gate and a floating region. The drift layer is of a first conductivity type. The first semiconductor region is of a second conductivity type and located on the drift layer, wherein the drift layer and the first semiconductor region have a stepped gate trench therein. The stepped gate trench at least comprises a first recess located in the first semiconductor region and extending into the drift layer and a second recess located below a bottom of the first recess, wherein a width of the second recess is smaller than a width of the first recess. A floating region is of the second conductivity type and located in the drift layer below the second recess.

主权项

1. A stepped trench MOSFET, comprising:
a drift layer of a first conductivity type; a first semiconductor region of a second conductivity type, disposed on a first surface of the drift layer, wherein a stepped gate trench is disposed in the drift layer and in the first semiconductor region, the stepped gate trench at least comprises a first recess and a second recess, the first recess is located in the first semiconductor region and extends into the drift layer, the second recess is located in the drift layer below a bottom of the first recess, and a width of the second recess is smaller than a width of the first recess; a second semiconductor region of the first conductivity type, disposed on a second surface of the drift layer; a stepped gate, disposed in the stepped gate trench; a floating region of the second conductivity type, disposed in the drift layer below a bottom of the second recess; an insulation layer, disposed in the stepped gate trench and insulating the stepped gate from each of the first semiconductor region, the drift layer and the floating region; and a source region of the first conductivity type, disposed in the first semiconductor region adjacent to a sidewall of the stepped gate trench, wherein a current conducting channel is formed in the first semiconductor region when a gate voltage (Vds) greater than a threshold voltage (Vth) is applied, along the sidewall of the stepped gate trench and between the source region and the drift layer.