Vertical rectifier with added intermediate region

A semiconductor rectifier device, comprising:

• a source region, near a first surface of a semiconductor material, having a first conductivity type;
• a body region having a second conductivity type, and underlying the source region;
• a drift region having a first conductivity type, and underlying the body region;
• an insulated gate trench extending down through the body region into the drift region;
• an intermediate region of the second conductivity type at the bottom of the gate trench within the drift region;
• a body contact region of the second conductivity type, extending down through the body region into the drift region;
• a first metallization layer at the first surface, connected to the source region, and body contact region, and the gate electrode;
• a second metallization layer, at a second surface which is opposite to the first surface, which is ohmically connected to the drift region;
• wherein, when the metallization layers are biased with a first polarity, majority carriers pass from the source region, through a portion of the body region which is inverted by capacitive coupling to the gate electrode, and therethrough into the drift region;
• wherein an additional first-conductivity-type doping is present near the bottom of the body region, to thereby increase conduction under forward bias;
• and wherein, when the metallization layers are biased with an opposite polarity, depletion regions in the drift region spread from the intermediate diffusion and from the body contact regions to pinch off conduction between the body region and the second metallization.

A method of operating a semiconductor rectifier, comprising the actions of:

• when forward bias is applied between an anode terminal and a cathode terminal, allowing majority carriers to flow
• from a first-conductivity-type source region near a first surface of a semiconductor die,
• through a channel portion of a second-conductivity-type body region which underlies the source region, and thence
• through a first-conductivity-type drift region, which underlies the body region, to a drain region at a second surface of the dies;
• wherein the channel region is capacitively coupled to a gate electrode in an insulated trench;
• and wherein the source and body regions, and the gate electrode, are all connected to one of the anode and cathode terminals;
• and when reverse bias is applied between the anode and cathode terminals, allowing depletion regions to spread into the drift region
• from a second-conductivity-type body contact region which extends down through the body region and into the drift region, and also
• from a second-conductivity-type intermediate region which lies at least partly below the gate trench,
• to merge, at a reverse bias short of breakdown, to pinch off conduction below the depth of the channel region, and thereby substantially prevent leakage current from flowing between the anode and cathode terminals;
• wherein an additional first-conductivity-type doping is present near the bottom of the body region, to thereby increase conduction under forward bias.