Multi-bit ROM cell with bi-directional read and a method for making thereof
US6870233B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 14, 2003 |
| Grant date | Mar 22, 2005 |
| Priority date | — |
| Expiry date | Aug 14, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH10B20/00
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A multi-bit Read Only Memory (ROM) cell has a semiconductor substrate of a first conductivity type with a first concentration. A first and second regions of a second conductivity type spaced apart from one another are in the substrate. A channel is between the first and second regions. The channel has three portions, a first portion, a second portion and a third portion. A gate is spaced apart and is insulated from at least the second portion of the channel. The ROM cell has one of a plurality of N possible states, where N is greater than 2. The possible states of the ROM cell are determined by the existence or absence of extensions or halos that are formed in the first portion of the channel and adjacent to the first region and/or in the third portion of the channel adjacent to the second region. These extensions and halos are formed at the same time that extensions or halos are formed in MOS transistors in other parts of the integrated circuit device, thereby reducing cost.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.