Analysis of submicron double-gated polysilicon MOS thin film transistors

Double-gated poly-Si MOS thin film transistors (TFTs), having two gate electrodes (top and bottom) connected together, are analyzed by the numerical solution of the Poisson equation. It is found that for fully inverted films there is a strong coupling of the top and bottom channels, resulting in a more efficient channel charge modulation and substantial improvement of electrical characteristics: reduction of subthreshold swing, reduction of threshold voltage, enhancement of drive current, and suppression of punch-through degradation in submicron channel length TFTs. By applying the double-gated structure, submicron poly Si PMOS TFTs have been realized with 0.6 mu m channel length, OFF current of 0.4 pA/ mu m, and ON/OFF ratio >5*15/sup 5/, demonstrating the applicability of this device in ULSI SRAM cells.<
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