United Microelectronics Corp.

Kuan-Te Pai

Yi-Min Jen

A method for manufacturing a trench isolation in a semiconductor device is disclosed, wherein a silicon nitride layer used as an anti-diffusion layer mask that defines an isolation region on a silicon substrate and a thermal oxidation process that is performed on active regions are previously used. A silicon substrate having a first pad oxide layer and a first silicon nitride layer formed thereon is first provided. Then the first pad oxide layer and the first silicon nitride layer are patterned to form an anti-diffusion layer mask and to expose an active region of the silicon substrate. Next the silicon substrate is oxidized to form a first silicon dioxide layer, wherein lateral oxidation on the active region of the silicon substrate underneath the first pad oxide layer and the first silicon nitride layer provides an edge of the first silicon dioxide layer in the shape of a bird's beak. Moreover, the first silicon nitride layer, the first pad oxide layer and the first silicon dioxide layer are removed to expose the silicon substrate. Furthermore, a second pad oxide layer is formed on the substrate and a second silicon nitride layer is deposited thereon. Finally, an isolation trench of the invention can be formed by using a conventional method.

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Kuan-Te Pai