A horizontal MOSFET prevents itself from breakdown caused by an avalanche current which flows to a base of a parasitic bipolar transistor when avalanche breakdown of a diode formed between a drain and a substrate occurs. A current path, comprised of a back electrode or a layer with high impurity concentration, is disposed on the side of a back surface of a semiconductor substrate. This current path reduces the base current of the parasitic transistor. Due to this, heat generation caused by an operation of the parasitic transistor is suppressed, and the avalanche withstand capability of the MOSFET is improved corresponding to reduction of the internal resistance component of the MOSFET.
A withstand voltage against electrostatic discharge of a high voltage MOS transistor is improved. An N.sup.- -type drain layer is not formed under an N.sup.+ -type drain layer, while a P.sup.+ -type buried layer is formed in a region under the N.sup.+ -type drain layer. A PN junction of high impurity concentration is formed between the N.sup.+ -type drain layer and the P.sup.+ -type buried layer. In other words, a region having low junction breakdown voltage is formed locally. The surge current flows through the PN junction into the silicon substrate before the N.sup.- -type drain layer below a gate electrode is thermally damaged. Hence, the ESD withstand voltage is improved.
The invention provides a semiconductor device exhibiting a stable and high breakdown voltage, which is manufactured at a low manufacturing cost. The semiconductor device of the invention includes an n-type silicon substrate; a p-type base region in the surface portion of substrate; an n-type drain region in the surface portion of n-type substrate; a p-type offset region in the surface portion of n-type substrate; an n-type source region in the surface portion of p-type base region; a p-type contact region in the surface portion of p-type base region; a gate electrode above the extended portion of p-type base region extending between n-type source region and n-type substrate (or p-type offset region), with a gate insulation film interposed therebetween; an insulation film on gate electrode and p-type offset region; a source electrode on n-type source region; and a drain electrode on n-type drain region. The p-type offset region is formed of a first p-type sub-region, a second p-type sub-region, and a third p-type sub-region.
The invention provides a semiconductor device exhibiting a stable and high breakdown voltage, which is manufactured at a low manufacturing cost. The semiconductor device of the invention includes an n-type silicon substrate; a p-type base region in the surface portion of substrate; an n-type drain region in the surface portion of n-type substrate; a p-type offset region in the surface portion of n-type substrate; an n-type source region in the surface portion of p-type base region; a p-type contact region in the surface portion of p-type base region; a gate electrode above the extended portion of p-type base region extending between n-type source region and n-type substrate (or p-type offset region), with a gate insulation film interposed therebetween; an insulation film on gate electrode and p-type offset region; a source electrode on n-type source region; and a drain electrode on n-type drain region. The p-type offset region is formed of a first p-type sub-region, a second p-type sub-region, and a third p-type sub-region.
A high voltage lateral semiconductor device for integrated circuits with improved breakdown voltage. The semiconductor device comprising a semiconductor body, an extended drain region formed in the semiconductor body, source and drain pockets, a top gate forming a pn junction with the extended drain region, an insulating layer on a surface of the semiconductor body and a gate formed on the insulating layer. In addition, a higher-doped pocket of semiconductor material is formed within the top gate region that has a higher integrated doping than the rest of the top gate region. This higher-doped pocket of semiconductor material does not totally deplete during device operation. Moreover, the gate controls, by field-effect, a flow of current through a channel formed laterally between the source pocket and a nearest point of the extended drain region.
A field effect transistor includes a substrate having a doping of a first conductivity type, a drain area in the substrate having a doping of a second conductivity type oppposite the first conductivity type, a source area in the substrate being laterally spaced from the drain area and having a doping of the second conductivity type, and a channel area in the substrate that is arranged between the source area and the drain area. In a portion of the substrate bordering the drain area, an area having a doping of the second conductivity type, which is connected to the drain area, is arranged such that in the portion alternating regions having the first conductivity type and having the second conductivity type are arranged.
