United Microelectronics Corp.

Hung-Yi Tsai

Shih-Yin Hsiao

Shan-Shi Huang

Tun-Jen Cheng

Ching-Wei Teng

Te-Chiu Tsai

A method for forming gate structures for a HV device and a MV device is provided. The method includes forming a HV oxide layer on the substrate, covering a first region predetermined for forming the HV device. Further in the method, a dielectric mask is formed on a central portion of the HV oxide layer. A thermal oxidation process is performed to form a MV oxide layer on the substrate at a second region predetermined for forming the MV device, wherein peripheral portions of the HV oxide layer not covered by the dielectric mask grow thicker. The dielectric mask is removed. A conductive layer is formed over the substrate. The conductive layer, the HV oxide layer, the MV oxide layer are patterned to form the gate structures.

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Taipei, Taiwan

Hung-Yi Tsai