Vertical MOSFET with dual work function materials
US7294879B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 18, 2003 |
| Grant date | Nov 13, 2007 |
| Priority date | — |
| Expiry date | Jul 6, 2025 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH10B12/0383
Abstract
A vertical pass transistor used in a DRAM cell for maintaining a low total leakage current and providing adequate drive current is described together with a method of fabricating such a device. The transistor gate is engineered in lieu of the channel. The vertical pass transistor for the DRAM cell incorporates two gate materials having different work functions. The gate material near the storage node is n-type doped polysilicon. The gate material near the bit line diffusion is made of silicide or metal having a higher work function than the n-polysilicon. The novel device structure shows several advantages: the channel doping is reduced while maintaining a high Vt and a low sub-threshold leakage current; the carrier mobility improves with the reduced channel doping; the body effect of the device is reduced which improves the write back current; and the sub-threshold swing is reduced because of the low channel doping.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.