Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Patent
1998-04-30
1999-01-26
Ngo, Ngan V.
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
257391, 257392, H01L 2976, H01L 2974, H01L 31062, H01L 31113
Patent
active
058641645
ABSTRACT:
A multi-stage read only memory (ROM) device and a method for fabricating the same. The device includes a source/drain pole and a gate in a trench, wherein the gate intersects the source/drain pole at an angle to form a number of memory cells. The fabrication of the multi-stage ROM includes two encoding processes. The first encoding process includes implantation of impurity ions in a portion of memory cells to adjust the threshold voltage, so that some of the memory cells have a first threshold voltage and the others have a second threshold voltage. The second encoding process includes forming a number of dielectric remainders at the bottom of the gate trench of a portion of the memory cells, so that some of the memory cells have a first effective channel width and the others have a second effective channel width. As a result, the memory cells of a ROM are of four types with different combinations of threshold voltages and effective channel widths.
REFERENCES:
patent: 5306941 (1994-04-01), Yoshida
patent: 5384478 (1995-01-01), Hong
patent: 5453637 (1995-09-01), Fong-Chun et al.
Ngo Ngan V.
United Microelectronics Corp.
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