Patent ID: 9530885
Filing Date: 2016-12-27
CPC Classification: H01L

Claim Text:
1. A normally on high voltage switch device (“normally on switch device”), comprising: a first semiconductor layer of a first conductivity type, the first semiconductor layer being heavily doped and forming a drain region of the normally on switch device; a second semiconductor layer of the first conductivity type formed on the first semiconductor layer; a first trench and a second trench formed spaced apart in the second semiconductor layer, each of the first trench and the second trench being lined with an insulating layer and filled with a conductive material to form a trench gate of the normally on switch device; a first doped region of a second conductivity type, opposite the first conductivity type, formed under the first trench in the second semiconductor layer and a third doped region of the second conductivity type formed under the second trench in the second semiconductor layer, the first and third doped regions being electrically connected to the conductive material in the respective first and second trenches to form a gate terminal of the normally on switch device; and a second doped region of the first conductivity type formed on a first surface of the second semiconductor layer between the first and second trenches, the second doped region being heavily doped and forming a source region of the normally on switch device, wherein the normally on switch device comprises a channel formed in the second semiconductor layer between the source region and the drain region and the channel has a width controlled by the gate terminal formed by the trench gate and the first and third doped regions, and in response to a reverse bias voltage being applied to the gate terminal relative to the source region, a depletion region is formed at the junction of the first and third doped regions and the second semiconductor layer to modulate the width of the channel and to pinch off the channel to switch off the normally on switch device.