Fixed resistance high density parallel ROM device
AssigneeHoltek Microelectronics, Inc.
InventorsChi-Yung Wu, Ling Chen, Tong Peng
Life of this patent
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Abstract
The present invention provides a fixed resistance sense-routed high density parallel ROM device for maintaining the resistance of a buried N+ region on a sense route constant. When data is read from a ROM cell matrix, the selection of different ROM cell transistors does not change the resistance of the buried N+ region on the sense route and thus enables a simplified design of a sense amplifier. The inactive select gate or transfer gate that is activated by the select line can be isolated by ion implantation for forming a buried P+ isolation and thus avoiding the narrowing or the cutting-off of the width of the active transfer gate or select gate due to ion diffusion.
Claims9
A fixed resistance high density parallel ROM device comprising:
- a plurality of word lines formed of more than one horizontal polysilicons, said polysilicons being parallel to each other;
- a plurality of bit lines, each of said bit lines being formed of a vertical buried N+ region, said plurality of bit lines being parallel to each other and perpendicularly crossing said word lines to form a ROM cell matrix;
- a plurality of metal conducting wires positioned on a surface of a top layer of every other of said buried N+ regions, each of said wires being connected to a metal contact;
- a plurality of select lines formed of polysilicons and situated above and below said ROM cell matrix for selecting a ROM region block;
- a plurality of buried N+ extension regions, each of said buried N+ extension regions being situated below said metal contact and extending into said metal line;
- and
- a plurality of ion implanted regions formed by ion implanting into buried P+ regions for insulating inactive select and transfer gates on said select lines.
Dependencies are inferred from the claim text.