Patent ID: 9029223
Filing Date: 2015-05-12
Classification: H01L

Abstract:
1. A method for fabricating a metal-oxide-semiconductor (MOS) device with isolated drain, comprising: providing a semiconductor substrate having a first conductivity type; forming a first well region embedded in a portion of the semiconductor substrate, having a second conductivity type opposite to the first conductivity type; forming a first patterned mask layer over the semiconductor substrate, exposing portions of the semiconductor substrate, wherein the portions of the semiconductor substrate are separated from each other by the first patterned mask layer; performing a first ion implant process on the portions of the semiconductor substrate exposed by the first patterned mask layer, forming a plurality of second well regions in the semiconductor substrate and defining a plurality of third well regions in the semiconductor substrate, wherein the second well regions and third well regions are interleaved and overlie the first well region, and the second well regions have the second conductivity type, and the third well regions have the first conductivity type; removing the first patterned mask layer and forming a second patterned mask layer over the semiconductor substrate, exposing one of the second well regions; performing a second ion implant process to the second well region exposed by the second patterned mask layer, forming a fourth well region between the first well region and the second well region, wherein the fourth well region is adjacent to a side of the third well region and has the first conductivity type; performing a third implant process to the second well region exposed by the second patterned mask layer, forming a fifth well region overlying the fourth well region and being adjacent to the third well region, wherein the fifth well region has the second conductivity type; removing the second patterned mask layer and forming a gate stack over the semiconductor substrate, covering a portion of the third and fifth well regions; forming a source region in a portion of the third well region; and forming a drain region in a portion of the fifth well region.