A power MOS device that has increased channel width comprises a semiconductor substrate and a doped upper layer of a first conduction type disposed on the substrate. The upper layer comprises a plurality of doped well regions of a second, opposite conduction type and a plurality of heavily doped source regions of the first conduction type at an etched upper surface of the upper layer that comprises parallel corrugations disposed transversely to the source regions. A gate that separates one source region from another comprises an insulating layer and a conductive material. The corrugations provide an increase in width of a channel underlying the gate and the well and source regions. In a process for forming a power MOS device with increased channel width on a semiconductor substrate having a doped upper layer of a first conduction type, a stripe mask is formed on an upper surface of the upper layer, and the upper surface is selectively etched to form a corrugated surface comprising a plurality of parallel corrugations. Following removal of the stripe mask, an insulating layer is formed on the corrugated surface, and an overlying conductive layer is formed on the insulating layer, the insulating and conductive layers comprising a corrugated gate region disposed transversely to the parallel corrugations of the upper surface. A dopant of a second, opposite conduction type is implanted to form a doped well region in the upper layer, and a dopant of the first conduction type is implanted into a portion of the corrugated surface adjacent to the gate, thereby forming a heavily doped source region in the upper layer. In an alternative procedure for forming a gate, a gate trench having a floor comprising parallel corrugations that substantially correspond to the corrugations in the upper surface is etched into the upper layer. Following lining of the trench floor and sidewalls with an insulating layer, the trench is substantially filled with a conductive material to form a gate trench. A dopant of the first conduction type is implanted into a portion of the corrugated surface adjacent to the gate region, thereby forming a heavily doped source region in the upper layer.