Recessed drift region for HVMOS breakdown improvement

A high-voltage metal-oxide-semiconductor (HVMOS) device having increased breakdown voltage and methods for forming the same are provided. The HVMOS device includes a semiconductor substrate; a gate dielectric on a surface of the semiconductor substrate; a gate electrode on the gate dielectric; a source/drain region adjacent and horizontally spaced apart from the gate electrode; and a recess in the semiconductor substrate and filled with a dielectric material. The recess is between the gate electrode and the source/drain region, and is horizontally spaced apart from the gate electrode.