A new high-side and low-side LDMOST with a selective buried layer in the substrate

•New LDMOST with an n-type selective buried layer in p-substrate is proposed.•The selective buried layer enhances low- and high-side breakdown voltage.•For given breakdown voltage, shorter drift length and less area are needed.•Electric field in both surface and bulk region are improved by the buried layer.•In high-side mode, drive-current is not alleviated due to depletion immunity of drift.