Patent ID: 8841721

Claim:
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.