| 摘要 |
PURPOSE:To contrive improvement in the intensity of alpha-ray resistance by a method wherein the impurity in the first buried layer, to be used for the first bipolar transistor, is made higher than the impurity density of the second buried layer to be used for the second bipolar transistor. CONSTITUTION:In the semiconductor substrate 1 such as a p-type Si substrate, an n<+> type buried layer 2 and a p<+> type channel stopper region 3 are provided, and an n-type Si epitaxial layer 4, for example, is provided on the substrate 1. The field insulating film 5 such as an SiO2 film is provided in the layer 4, and the isolation between elements and inside the elements is performed. A p<+> type base region 6 is provided on the prescribed part of said epitaxial layer 4 located in a memory cell part, a p<+> type polycrystalline Si film 9 is connected to the side face of the base region 6 through the intermediary of a p<+> type graft base region 8, and npn type bipolar transistor 10 of reverse direction, to be used for memory cell, is composed of the emitter region consisting of the above-mentioned buried layer 2, the base region 6 and the collector region 7. The forward direction and reverse direction npn type bipolar transistors 10 and 22 have the impurity density profile different with each other, and the optimization of their characteristics can be achieved. |
