A semiconductor device, such as a metal-oxide semiconductor field-effect transistor, includes a semiconductor substrate, a drift layer formed on the substrate, a first and a second source region, and a JFET region defined between the first and the second source regions. The JFET region may have a short width and/or a higher concentration of impurities than the drift layer. The semiconductor device may also include a current spreading layer formed on the drift layer. The current spreading layer may also have a higher concentration of impurities than the drift layer.