a lateral double diffused metal oxide semiconductor device , and method of fabricating such a device , are provided . the method comprises the steps of : providing a substrate of a first conductivity type ; forming within the substrate a well region of a second conductivity type , the well region having a super steep retrograde well profile in which a doping concentration changes with depth so as to provide a lighter doping concentration in a surface region of the well region than in a region below the surface region of the well region ; forming a gate layer which partly overlies the well region and is insulated from the well region ; and forming one of a source region and a drain region in the well region . the presence of the ssr well region provides a lighter surface doping to enable a higher breakdown voltage to be obtained within the ldmos device , and heavier sub - surface doping to decrease the on - resistance .