| 摘要 |
PURPOSE:To offer the titled element double-diffused of high withstand voltage and high reliability. CONSTITUTION:When e.g. phosphorus is diffused through a diffusion window 9 in the main surface 8 of a semiconductor substrate 1, it is dispersed from the diffused window 9 to the periphery in the surface beside in the depth direction into a Pn junction 4a, and the area inside the Pn junction 4a becomes the first diffused region 2a. Successively, an impurity element forming the second diffused region 3a, e.g. boron is diffused through the same window 9 more shallowly than the first diffused region 2a, and a Pn junction 5a is formed between a dot line 9 indicating the edge of the diffusion window and the Pn junction 4a. Then, since the impurity concentration is on the decrease at a given gradient between the dot line 9 and the Pn junction 4a, the Pn junctions 5a of the second diffused region 3a is formed in the distribution of a given gradient in the surface as well as in the depth direction. Accordingly, the impurity concentration in the surface 8 in the neighborhood of the Pn junction 5a decreases; therefore, the reverse withstand voltage of this Pn junction 5a increases relatively. |
