| 摘要 |
PURPOSE:To make a junction breakdown type PROM higher in density as well as improve and equalize the writing characteristics, by forming a thin oxide film in a plain region surounded with a thick buried oxide layer, opening the thin film, diffusing shallowly an impurity and forming a junction of cell pants. CONSTITUTION:An N epitaxiall layer 3 is formed on a P substrate 1 provided with an N<+> type buried layer 2. The junction is separated to form an island region 3'. Then an oxidized film 5 is formed by using a mask of a nitride film 11. After a P base 6 is formed by ion injection, etching is so performed that the nitride film 11 is left in the emitter region, and a selective oxidization is performed again to form an oxide film 13. Then, by, for example, a plasma ethcing, the emitter region is opened to provide a polycrystalline Si layer 14. Then, for example, phosphorus is diffused to form a shallow emitter layer 7, and an Al electrode 15 is provided on the Si layer 14 to obtain a memory cell. Thereby, a precise shallow and small junction of the cell pants not influenced by the buried oxide film 5 can be obtained, and a compact device operable at low voltage and having a small writing characteristic fluctuation due to junction breakdown can be formed. |
