| 摘要 |
PURPOSE:To reduce sufficiently ON resistance, by forming a second conductivity type epitaxial layer of high resistance on a second conductivity type substrate of low resistance whose diffusion coefficient is small, constituting a gentle concentration distribution of impurity between the substrate and the epitaxial layer, and making the thickness of the epitaxial layer thin. CONSTITUTION:Between a second coductivity type substrate 21 of low resistance whose diffusion coefficient is small and a second conductivity type epitaxial layer 22 of high resistance, a second conductivity type buffer layer 10 of comparatively low resistance whose diffusion coefficient is large is formed in such a manner as to largely protrude in the epitaxial layer 22 side, and a protruding region 11 is formed to constitute a gentle impurity concentration distribution between the substrate 21 and the epitaxial layer 22. Breakdown voltage is maintained by the gradient of impurity concentration distribution, and the thickness of the epitaxial layer 22 is made about one-half of prior ones. By decreasing resistance REpi, the ON resistance Ron of an element constitution can be sufficiently reduced. |
