American Microsystems, Inc.

Thurman J Rodgers

James D Trotter

A semiconductor programmable read only memory device (PROM) utilizes an array of memory cells each having an area basically defined by the intersection of a bit line and a word address line. On a substrate of one conductivity type is an upper layer of material of the opposite conductivity within which are diffused bit lines of the same conductivity material as the substrate. The crossing address lines are conductive material formed on an insulating layer that covers the diffused bit lines and the upper layer. Each cell is a single transistor element in the form of a V-type MOSFET which achieves the normal AND function (Data-Word Address) using a capacitance coupled version of threshold logic. Each MOSFET is formed by a V-shaped recess at the intersection of each bit line and address line that extends through the diffused bit line, (which serves as the transistor drain) and into the substrate (which serves as the source and ground plane of the device). A similarly V-shaped floating gate is isolated below and above the crossing bit and address lines by thin oxide layers. Data is written into the cell when hot electrons are injected into the gate oxide near the drain junction and attracted to the floating gate which has been charged positive by capacitance coupling from the word line. The hot electrons are generated from the channel current via impact ionization at the pinched-off drain junction.

VMOS Floating gate memory device

A semiconductor electrically programmable read only memory device (EPROM) utilizes an array of memory cells each in the form of a single V-type MOSFET which achieves the normal AND function (Data-Word Address) using a capacitance coupled version of threshold logic. Each MOSFET is formed by a V-shaped recess at the intersection of each bit line and word line that extends across the diffused bit line, (which serves as the transistor drain) and into the substrate (which serves as the source and ground plane of the device). A similarly V-shaped floating gate is isolated below and above the crossing bit and word lines by thin oxide layers. A ring of P-type conductive material around the upper end of each V-shaped recess and adjacent its surrounding N-type drain region serves to lower the required programming voltage without increasing the device threshold voltage.

VMOS Floating gate memory with breakdown voltage lowering region

An MOS transistor is provided having a surface diffused drain and a common substrate source. A heavily doped base layer and a lightly doped space charge region are provided between the drain and source regions. The gate is formed on the inclined surface of a V groove which penetrates into the transistor to the substrate exposing the base layer to the gate structure. The gate is formed in the V groove by a silicon oxide insulative layer and conductive layer. Appropriate leads contact the gate conductor and the drain.

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Palo Alto, CA, United States of America

Thurman J Rodgers