LDD method of coding mask ROM device and LDD coded mask ROM devi

Details LDD method of coding mask ROM device and LDD coded mask ROM devi LDD method of coding mask ROM device and LDD coded mask ROM devi

1995-08-03

1996-07-23

Chaudhari, Chandra

Fishing, trapping, and vermin destroying

437 34, 437 44, H01L 218246

Patent

active

055389147

ABSTRACT:
A CMOS Mask ROM semiconductor device is formed in P-well NMOS region of a silicon semiconductor substrate with FOX regions on the surface thereof. A method of forming the device includes forming gate oxide over the substrate between FOX regions; forming a control gate layer over the gate oxide. Then form a gate mask over the device with and pattern a gate electrode and the gate oxide layer by etching through mask openings. Next, form an LDD mask over the device exposing the gate. Ion implant a P type dopant of a first dosage level through mask openings forming reverse type LDD implant doped P type regions. Form spacers adjacent to the electrode over the substrate. Ion implant an N type dopant of a second dosage level through the opening in the mask and aside from the spacers and the electrode into exposed portions of the substrate. The N type doped regions are thus self-aligned with the spacers and the gate and they provide a second dosage level in the substrate, the second dosage level being substantially different from the first dosage level.

REFERENCES:
patent: 4892841 (1990-01-01), Iwase et al.
patent: 5002896 (1991-03-01), Naruke
patent: 5091329 (1992-02-01), Bekkering et al.
patent: 5200355 (1993-04-01), Choi et al.

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