US 4,788,580 AGranted

Semiconductor memory and method of manufacturing the same

AssigneeMitsubishi Denki Kabushiki Kaisha

InventorKazutami Arimoto

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Abstract

A semiconductor memory comprises a p.sup.- -type semiconductor substrate (1), a p-type epitaxial layer (15) and p.sup.+ -type epitaxial layers (16, 17) formed thereon, an n.sup.+ -type region (6) formed on the p.sup.+ -type epitaxial layer (16) to serve as a bit line, an n.sup.+ -type region (5) formed on the p.sup.+ -type epitaxial layer (17) to serve as a charge storage region and a gate electrode (9) formed on the p-type epitaxial layer (15) to serve as a word line. The p.sup.+ -type epitaxial layers (16, 17) prevent passage of electrons within electron-hole pairs induced by alpha rays, to suppress occurrence of soft errors. The p-type epitaxial layer (15) defines a region corresponding to the channel region of a bus transistor, whereby the impurity concentration thereof can be easily controlled, to readily set the threshold voltage of the bus transistor at an appropriate level.

Claims8

Dependent claims

A semiconductor memory comprising:

a first conductivity type semiconductor substrate (1);
a first conductivity type first epitaxial layer (15) formed on said semiconductor substrate and being higher in impurity concentration than said semiconductor substrate, said first epitaxial layer defining a channel region;
at least two first conductivity type second epitaxial layers (16, 17) adapted to be separated by said first epitaxial layer defining said channel region, said second epitaxial layers being higher in impurity concentration than said first epitaxial layer;
a second conductivity type second region (6) formed on one of said second epitaxial layers to serve as a bit line;
a second conductivity type third region (5) formed on the other one of said second epitaxial layers to serve as a charge storage region;
a first gate electrode (9) formed on said portion of said first epitaxial layer defining said channel region to serve as a word line;
and
a second gate electrode (8) formed on said second conductivity type third region to supply constant voltage.

5 more elements

Dependencies are inferred from the claim text.