Semiconductor device having retrograde well and diffusion-type w

Details Semiconductor device having retrograde well and diffusion-type w Semiconductor device having retrograde well and diffusion-type w

1993-06-03

1995-06-27

Larkins, William D.

Active solid-state devices (e.g., transistors, solid-state diode

Field effect device

Having insulated electrode

257374, 257396, 257657, H01L 27092, H01L 27108

Patent

active

054282390

ABSTRACT:
A DRAM is formed on a silicon substrate having a retrograde well and a diffusion-type well. The retrograde well has an impurity concentration profile which is set in steps by a plurality of ion-implantations. The diffusion-type well has an impurity concentration profile which changes monotonously by a thermal diffusion. A memory cell array is formed in the retrograde well region. A peripheral circuit is formed in the diffusion-type well region. The retrograde well enhances integration of devices included in the memory cell array. The diffusion-type well enhances the characteristic of insulating isolation between devices.

REFERENCES:
patent: 4411058 (1983-10-01), Chen
patent: 4907058 (1990-03-01), Sakai
"An Experimental 1-Mbit BiCMOS DRAM", Kitsukawa et al., IEEE Journal of Solid-State Circuits, vol. SC-22, No. 5, Oct. 1987, pp. 657-662.
"A 0.5 .mu.m Isolation Technology Using Advanced Poly Silicon Pad LOCOS (Appl)," IEDM '88, pp. 100-103.
"An Advanced Half-Micrometer CMOS Device with Self-Aligned Retrograde Twin-Wells and Buried P.sup.+ Layer," VLSI Symposium, 1989.
"A New Twin-Well CMOS Process Using Nitridized-Oxide-LOCOS (NOLOCOS) Isolation Technology," IEEE Electron Device Letters, vol. 10, No. 7, Jul., 1989, pp. 307-309.

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