A new MOS gate-controlled power switch with a very low on-resistance is described. The fabrication process is similar to that of an n-channel power MOSFET but employs an n-epitaxial layer grown on a p+ substrate. In operation, the epitaxial region is conductivity modulated (by excess holes and electrons) thereby eliminating a major component of the on-resistance. For example, on-resistance values have been reduced by a factor of about 10 compared with those of conventional n-channel power MOSFETs of comparable size and voltage capability.