| 摘要 |
A high concentration n-type semiconductor region (21) having a width (W) and a distance (D) of constant ranges is selectively formed to be overlapped with or adjacent to a buffer layer (2). When a thickness (L) of an n-type semiconductor layer (3) is 50 mu m and the distance (D) is 3 mu m, for example, the width (W) is set in the range of 3 mu m to 7 mu m. In this case, a saturation voltage (VCE(sat)) and a fall time (tf) are improved best as compared with a conventional device having no high concentration n-type semiconductor region (21). Thus, the saturation voltage (VCE(sat)) and the fall time (tf) are compatibly reduced.
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