Lateral high breakdown voltage MOSFET and device provided therewith
View Patent ↗A film thickness of a gate oxide film of a lateral high breakdown voltage MOSFET of a first conduction type is formed with a thickness in which an electric field value to an absolute maximum rated voltage between a source and a drain becomes equal to or less than 4 MV/cm, and a drain diffused layer is formed so that a total amount of impurities therein becomes equal to or more than 2×10 12 /cm 2 to reduce an on-resistance of the lateral high breakdown voltage MOSFET while ensuring a breakdown voltage thereof, and to reduce an area of the lateral high breakdown voltage MOSFET.
1. A semiconductor device, comprising:
a lateral high breakdown voltage MOSFET comprising
a buried layer formed in a region of a semiconductor substrate,
a drain diffused layer formed on a surface side on the buried layer,
a body diffused layer formed by diffusion on the surface side on the buried layer surrounding the drain diffused layer,
a source diffused layer formed in the body diffused layer at a specified distance from a boundary of the drain diffused layer,
a drain contact diffused layer formed on a surface side of the drain diffused layer,
a gate oxide film formed on a surface of the body diffused layer, from an end of the source diffused layer over a portion of the drain diffused layer,
a field oxide film formed on the surface of the drain diffused layer, in a region without the drain contact diffused layer and the gate oxide film, and
a gate electrode formed above the gate oxide film over a portion of the field oxide film, wherein the gate oxide film comprises a thickness in which an electric field value of an absolute maximum rated voltage between a source and a drain is equal to or less than 4MV/cm, and a total amount of impurities in the drain diffused layer is equal to or more than 2×10 12 /cm 2 ; and
a lateral low breakdown voltage MOSFET.
2. The lateral high breakdown voltage MOSFET as recited in claim 1 , wherein the drain diffused layer, the source diffused layer, and the drain contact diffused layer are of a first conduction type and the body diffused layer and the semiconductor substrate are of a second conduction type.
3. The semiconductor device as recited in claim 1 , wherein the lateral low breakdown voltage MOSFET is simultaneously formed in a diffused layer with the drain diffused layer.
4. The semiconductor device as recited in claim 1 , wherein the lateral low breakdown voltage MOSFET is simultaneously formed in a diffused layer with the body diffused layer.
5. The semiconductor device as recited in claim 1 , further comprising:
a first lateral low breakdown voltage MOSFET of a first conduction type simultaneously formed in a diffused layer with the body diffused layer; and
a second lateral low breakdown voltage MOSFET of a second conduction type simultaneously formed in the diffused layer with the drain diffused layer, where the first and second lateral low breakdown voltage MOSFETs form a CMOS circuit.
6. The lateral high breakdown voltage MOSFET as recited in claim 1 , wherein a distance between the source diffused layer and the drain diffused layer is longer than a projected length of the drain diffused layer from the drain contact diffused layer.
7. The lateral high breakdown voltage MOSFET as recited in claim 1 , wherein a length of the gate electrode on the field oxide film is equal to or less than 2 mm.
8. The lateral high breakdown voltage MOSFET as recited in claim 1 , wherein widths of depletion layers on an uppermost surface side of a semiconductor layer are W 1 <W 2 when a reverse bias voltage is applied between the source and the drain,
where W 1 is a width of one of the depletion layers extending toward a side of the drain diffused layer, and
W 2 is a width of another of the depletion layers extending toward a side of the body diffused layer.
9. The lateral high breakdown voltage MOSFET as recited in claim 1 , wherein the lateral high breakdown voltage MOSFET is a lateral low breakdown voltage MOSFET of a first conduction type and is simultaneously formed in a diffused layer with the body diffused layer of a second conduction type.
10. The lateral high breakdown voltage MOSFET as recited in claim 1 , wherein a lateral low breakdown voltage MOSFET of a second conduction type is simultaneously formed in a diffused layer with the drain diffused layer of a first conduction type, a lateral low breakdown voltage MOSFET of the first conduction type is formed in a diffused layer simultaneously formed with the body diffused layer of the second conduction type, and the low breakdown voltage MOSFETs of the first and second conduction types form a CMOS circuit.