Takuji Matsumoto

Novel SOI wafer engineering using low stress and high mobility CMOSFET with -channel for embedded RF/analog applications

For high performance RF/analog and logic device technology, novel SOI wafer engineering featuring <100>-channel SOI CMOSFET with high-resistivity substrate is proposed. Mobility of PMOSFET is improved about 16% by changing a channel direction from <110> to <100>. Moreover, the reduction of the drive current in narrow channel PMOSFET is suppressed. The maximum oscillation frequency (f/sub max/) for NMOSFET is improved around 7% by changing the buried oxide (BOX) thickness from 400 nm to 150 nm because the self-heating effect is suppressed, and is improved around 5% by changing the substrate resistivity from 10 /spl Omega/cm to 1000 /spl Omega/cm because the power loss is reduced. In this work, the wafer engineering which consists of 1) <100>-channel, 2) optimization of BOX, and 3) high resistivity substrate, is proposed to improve the RF performance of the CMOSFET.

70 nm SOI-CMOS of 135 GHz f/sub max/ with dual offset-implanted source-drain extension structure for RF/analog and logic applications

We achieved 135 GHz f/sub max/ and 10.98 dB MSG at 40 GHz, which represent the world record data in CMOS published papers, by using a 70 nm body-tied partially-depleted (PD) SOI-CMOS with offset-implanted source-drain extension (SDE) and thick cobalt salicide. The suppression of V/sub th/ variations was also realized due to this structure. Dual offset-implanted SDE structure was proposed to realize high performance of both RF/analog and logic applications. We found that the optimized offset gate spacer width of the RF/analog parts is different from that of the logic parts.

Clarification of floating-body effects on drive current and short channel effect in deep sub-0.25 /spl mu/m partially depleted SOI MOSFETs

We point out for the first time that floating-body effects cause the reduction of the saturation drive current in partially depleted (PD) Sol MOSFETs. It is demonstrated that when the channel concentration of the SOI MOSFETs is set higher in order to suppress the increase of the off current caused by floating-body effects, the drive current decreases due to the large body effect. In the conventional SOI structure where the source-drain junction is in contact with the buried oxide, the 0.18 /spl mu/m floating PD SOI MOSFET suffers around 17% decrease in the drive current under the same threshold voltage (V/sub th/) in comparison with body-fixed one. However, floating ID SOI MOSFETs show smaller V/sub th/-roll-off. Further considering the short channel effect down to the minimum gate length of 0.16 /spl mu/m, the current decrease becomes 6%. Also, we propose a floating PD SOI MOSFET with shallow source-drain junction (SSD) structure to suppress the floating-body effects. By using the SSD structure, we confirmed an increase in the drive current.