Method of fabricating lateral double diffused MOS (LDMOS) transistors

摘要

A process for the fabrication of an improved LDMOS transistor, and such an improved LDMOS transistor are provided. The improved LDMOS transistor is in a semiconductor layer of a first conductivity type. The transistor has a source and drain of a second conductivity type (opposite the first conductivity type) and a channel of the first conductivity type with a conductive gate insulatively disposed over the channel. A low-voltage tank of the second conductivity type is used to contain the drain drift region and because of its lower sheet resistance provides a lower RDS(on). This tank of the second conductivity type extends from the field oxide at the exterior perimeter of the drain region, joins with the channel region and extends below the gate oxide and field oxide associated therewith. Optionally, a high-voltage tank of the second conductivity type is used to contain the entire area of the device, including the first tank of the second conductivity type, and isolate it from the substrate to provide a high breakdown voltage. The transistor without the optional high-voltage tank is particularly appropriate for use as the low-side driver (LSD) portion of an H-bridge. For the high-side driver (HSD) portion of an H-bridge the device with the optional high-voltage tank of the second conductivity type is used. The LSD and HSD devices of the present invention may also be used as separate stand-alone devices.