Method of forming vertical mosfet device having voltage clamped gate and self-aligned contact
US6268242A · kind A · utility
Inventors
Key dates
| Filing date | May 19, 1999 |
| Grant date | Jul 31, 2001 |
| Priority date | — |
| Expiry date | May 19, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01L2924/0002
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
One or more diodes are connected in a conductive path between the source and gate of a vertical MOSFET to prevent the voltage between the gate and source from exceeding a predetermined level and thereby protect the gate oxide layer from damage. The diodes are formed in the same polysilicon layer that is used to form the gate of the MOSFET, by implanting N and P-type dopants into the layer. To minimize the number of additional processing steps required, at least one of these implants is performed simultaneously with the implanting of the source or body of the MOSFET. As an additional aspect of the invention, the metal contact to the source and body regions in a vertical planar DMOSFET is formed by fabricating a sidewall spacer on the gate of the MOSFET. With the metal contact self-aligned to the gate in this way, the lateral dimension of each of the cells in the DMOSFET can be significantly reduced without the risk of a short between the contact and the gate, and the packing density of the cells can be increased. In this way, significant reductions in the on-resistance of the device can be achieved.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.