SEMICONDUCTOR DEVICE AND MANUFACTURE THEREOF

摘要

PURPOSE:To make a semiconductor device stable in distribution of a surface electrical field so as to improve it in reliability to breakdown strength and to widen the thickness and the impurity concentration of a first semiconductor region in allowable range so as to improve the semiconductor device in degree of freedom of design. CONSTITUTION:An N<-> epitaxial layer 32 is formed on a P<-> semiconductor substrate 31, and a P diffusion region 33 is formed in the epitaxial layer 32 so as to reach to the P<-> semiconductor substrate 31 extending from the surface of the layer 32. An N<+> diffusion region 34 and a P diffusion region 35 are formed on the surface of the N<-> epitaxial layer 32. A conductive film 37 is formed on the surface of the N<-> epitaxial layer 32 between the P diffusion regions 33 and 35 through the intermediary of a comparatively thin insulating film 36. The conductive film 37 and the P diffusion region 35 are made to function as a composite field plate, a depletion layer is made to extend laterally further on the surface of the N<-> epitaxial layer 32 through the influence of the electrical field generated from the composite field plate concerned, whereby a surface electrical field is relaxed and a diode is improved in breakdown strength.