Semiconductor device having retrograde well and diffusion-type well
US5428239A · kind A · utility
33Cited by
2References
8Claims
0Family size
Assignee
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Key dates
| Filing date | Jun 3, 1993 |
| Grant date | Jun 27, 1995 |
| Priority date | — |
| Expiry date | Jun 3, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH10D84/859
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.