US 5,510,630 A · Non-volatile random access memory cell constructed of silicon carbide

Abstract

A non-volatile random access memory (NVRAM) cell that utilizes a simple, single-transistor DRAM cell configuration. The present NVRAM employs an enhancement mode nMOS transistor made as an accumulation mode transistor. The transistor has an n-type silicon carbide channel layer on a p-type silicon carbide buffer layer, with the channel and buffer layers being on a highly resistive silicon carbide substrate. The transistor also has n+ source and drain contact regions on the channel layer. A polysilicon/oxide/metal capacitor is preferably used which has a very low leakage current. Furthermore, this type of capacitor can be stacked on top of the transistor to save area and achieve high cell density. It is preferred to use a non-reentrant (edgeless) gate transistor structure to further reduce edge effects.

Claims24

Dependent claims

A nonvolatile random access memory cell, comprising:

a bit line for writing information to storage when a potential is applied to the bit line;
means for storing charge;
and
an accumulation mode MOSFET for connecting the charge storage means to the bit line, wherein the MOSFET is comprised of:
(i) a semi-insulating silicon carbide substrate;
(ii) at least one layer of p type silicon carbide provided upon the substrate;
(iii) a channel layer of n type silicon carbide provided on the at least one layer of p type silicon carbide;
(iv) two contact regions of n+ type silicon carbide, each contact region being spacedly provided upon the channel layer, such that the contact regions are separated a selected distance apart;
(v) a layer of an oxide provided upon the channel region of the n type channel layer between the two,contact regions;
and
(vi) a gate of conductive material provided upon the layer of the oxide.

8 more elements

Dependencies are inferred from the claim text.

Non-volatile random access memory cell constructed of silicon carbide

Life of this patent

Non-volatile random access memory cell constructed of silicon carbide

Life of this patent

Abstract

Claims24