JPS5456384A - Bipolar type programmable rom - Google Patents

Abstract

PURPOSE: To obtain a rewritabls programmable ROM by providing floating electrodes on the side face of base layer by way of insulation film and controlling the generation and annihilation of inversion layer depending upon the presence or absence of the voltage to be applied thereto.

CONSTITUTION: An N⁺ type buried region 2 and p⁺ type isolating regions 4 are respectively diffusion formed on a p type semiconductor substrate 1, and an N type layer 3 which becomes collector layer is epitaxially grown over the entire surface. Next, a P type impurity is diffused over the entire surface of the surface layer part of the layer 3 to provide a p type base layer 5 and an N type impurity is diffused over the entire surface to provide an N type emitter layer 6. The formed SiO₂ film 7 is covered with a Si₃N₄ film 12. Thereafter, the required portions of the films 7 and 12 are removed and are then etched to expose the junction between base and emitter and the junction between base and collector in convex form. The film is renewd to a new insulation film 7. Next, a polycrystalline Si layer 10 which becomes convex form is grown over the entire surface and with a photo resist film 13 as a mask, said layer is etched to expose the surface of the emitter layer 6. Thereafter, Al floating electrodes are mounted here to provide a memory cell

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