Semiconductor device

摘要

A semiconductor device has a well region formed in the surface of a substrate, and has semiconductor elements such as MOSFETs and bipolar transistors formed in the well region. The carrier concentration profile of the well region assumes the shape of a valley in the direction of depth thereof, and a minimum point thereof has a concentration of smaller than 5x1015 cm-3 and is located at a position within 1.6 mu m from the surface of the substrate. Preferably, the minimum point should have a concentration of greater than 5x1014 cm-3 but smaller than 5x1015 cm-3, and more preferably a concentration of greater than 1x1015 cm-3 but smaller than 5x1015 cm-3.