High breakdown voltage semiconductor device

摘要

A high breakdown voltage semiconductor device includes a semiconductor substrate, a first insulating film formed on the semiconductor substrate, a first semiconductor region formed on the first insulating film, a second semiconductor region of a first conductivity type having an impurity concentration higher than that of the first semiconductor region and selectively formed on a surface portion of the first semiconductor region, a third semiconductor region having an impurity concentration lower than that of the second semiconductor region and formed on the surface portion of the first semiconductor region so as to be adjacent to or near the second semiconductor region and a fourth semiconductor region of a second conductivity type having an impurity concentration higher than that of the first semiconductor region and formed on the surface portion of the first semiconductor region so as to be outside the third semiconductor region. A fifth semiconductor region having an impurity concentration lower than that of the second or fourth semiconductor region is formed on a bottom portion of the first semiconductor region. When a reverse bias is applied between the second and fourth semiconductor regions, a depletion layer extends vertically in the first semiconductor region and laterally in the fifth semiconductor region. The applied voltage is divided in both the directions and a high breakdown voltage can be obtained.