Taiwan Semiconductor Manufacturing Comp. Ltd.

Jun-Ker Yeh

Kuo-Sheng Chuang

Long-Sheng Yeou

Siu-Han Liao

The present invention provides a method for forming a transistor having a stacked gate electrode structure with two gates; a lower floating gate and an upper control gate. The floating gate is formed of three polysilicon layers--undoped/doped/undoped polysilicon layers. A substrate is provided having a tunnel oxide layer 20. Then sequentially a first undoped, first doped, and second undoped polysilicon layers 22,24,26 are formed over the tunnel oxide layer thereby forming a lower floating gate layer 22, 24, 26. An intergate dielectric layer 28,30,32 is then formed over the second undoped polysilicon layer 26. Next, an upper control gate 36 and a cap oxide layer are formed over the intergate dielectric layer 28,30,32. The stacked two gate electrode structure is formed by patterning the above mentioned layers. Then spaced source and drain regions 44 are formed on opposite sides of the stacked gate structure thereby completing the transistor.

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Hsin Chu, Taiwan

Jun-Ker Yeh