Semiconductor memory device
AssigneeFujitsu Limited
InventorsYasuhisa Sugo, Tohru Takeshima
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Abstract
A semiconductor memory device in which a bipolar memory cell includes two cross-coupled transistors. The collector load is a Schottky barrier diode. A capacitor is formed to be connected to the Schottky barrier diode. The capacitor is formed by a junction between a P.sup.+ -type diffusion region and an N.sup.+ -type buried layer functioning as a collector of the transistor. The P.sup.+ -type diffusion region is formed in the periphery of the Schottky barrier diode and between a metal layer connected to a word line and the N.sup.+ -type buried layer. By the capacitor, the stability of the memory holding state is improved without deteriorating the operating speed of the memory cell.
Claims8
A semiconductor memory device comprising:
- a plurality of word lines;
- a plurality of bit lines intersecting to said word lines;
- bipolar memory cells arranged on intersecting portions between said word lines and said bit lines;
- each of said bipolar memory cells comprising a first transistor, a second transistor, and a load connected between the collector of each of said first transistor and said second transistor and one of said word lines;
- the base and the collector of said first transistor being respectively connected to the collector and the base of said second transistor;
- said load comprising a Schottky barrier diode and a load resistor connected in parallel;
- said load further comprising a capacitor connected in parallel with said Schottky barrier diode;
- each of said first transistor and said second transistor comprising a semiconductor layer having a first conductivity type and operatively functioning as a collector region;
- and
- a high concentration buried layer formed in said semiconductor layer and having said first conductivity type;
- said Schottky barrier diode comprising a Schottky barrier region formed at the surface of said semiconductor layer;
- in said Schottky barrier region, a semiconductor region having a second conductivity type being formed so as to reach said high concentration buried layer;
- said capacitor being formed by a junction between said semiconductor region and said high concentration buried layer.
Dependencies are inferred from the claim text.