| 摘要 |
PURPOSE:To prevent any defective writing-in from occuring without cutting down the access time by a method wherein the impurity concentration in a semiconductor substrate forming a PROM is increased while the junction capacity of a buried layer to be a word line with the substrate is reduced. CONSTITUTION:A P<-> epitaxial layer 2, an N<+> buried layer 3 to be a word line, an N<-> epitaxial collector layer 5 are formed on a P<+> type substrate 1 while grooves reaching the P<->layer 2 are made to form P<+>regions 13 on the bottom thereof. The grooves are filled with oxide films 10, etc., to be interlayer insulating regions 6. Besides, P<+> regions 17 connected to the P<+>regions 13 for leading out substrate potential are formed. P<+> base regions 7, N<+> emitter regions 8 are formed in element regions while unit memory cells Q11, Q12 are connected in series by digit line D. In such a constitution, the base potential of parasitic NPN transistor formed between unit elements is not raised even if the unit memory cells are supplied with writing-in current due to the low resistance in the substrate 1 to minimize the leakage current resultantly preventing any defective writing-in from occuring. |
