New grooved-gate MOSFET with drain separated from channel implanted region (DSC)

Abstract
A new grooved-gate MOSFET with its drain separated from channel implanted regions (DSC structure) is proposed for the purpose of obtaining higher breakdown voltages: drain sustaining voltage and highest applicable voltage placed by hot-carrier effects. Nonimplanted regions between channel implanted and source/drain regions are a unique feature of this device structure. The self-aligned nonimplanted region in the channel is obtained by using silicon dioxide and resist overhangs. These overhangs are fabricated by grooving the silicon substrate. The DSC structure helps reduce the electric field at the drain. Characteristics of experimental devices are presented and compared with those of conventional MOSFET's, from the viewpoint of overall VLSI device design. This device structure is shown to provide remarkable improvements, achieving a 3- or 4-V increase in drain sustaining voltage, as well as a 1- or 2-V increase in the highest applicable voltage as limited by hot-electron injection. In addition, the proposed device can alleviate such short-channel effects as Vthlowering, and in particular, diminish narrow-channel effects. The influence of nonimplanted length on breakdown voltage is also clarified using the CADDET, two-dimensional analysis program.

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