| 摘要 |
PURPOSE:To suppress the gain of a pnp transistor in a bipolar LSI to be small and to prevent the malfunction of the LSI such as a latch-up or the like by a method wherein PSG is left on the side face of an opening part formed in a silicon oxide film on a substrate and impurities are implanted into the opening part and heat-treated. CONSTITUTION:A silicon oxide film 2 is formed on a silicon substrate 1 of a first conductivity type; after that, the silicon oxide film 2 in a position where a buried diffusion region 4 of a second conductivity type is to be formed on the substrate 1 is removed. Thereby, an opening part is formed. PSG is deposited in the opening part and on the silicon film 2 which has been left; thence, it is etched. Thereby, the PSG 3 is left only on the side face of the opening part. After that, impurities of the second conductivity type are implanted into the opening part; after that, they are heat-treated. Thereby, phosphorus is diffused from the PSG, the local concentration of a base region for a parasitic pnp transistor becomes very high and the gain of the parasitic pnp transistor is reduced remarkably.
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