National Yang Ming Chiao Tung University

Li-Tien Hsueh

Bing-Yue Tsui

Jui-Cheng Wang

Jui-Tse Hsiao

A gate fabrication method of an UMOSFET and a trench gate structure formed thereof are provided, comprising providing a transistor structure and a lithography process is employed to define a trench region. A gate oxide layer is deposited along the trench and two polysilicon sidewalls having a spacing there in between are formed afterwards. A wet etching is used to remove the gate oxide layer underneath the polysilicon sidewalls such that a vacancy is formed at the trench bottom. By oxidizing the polysilicon sidewalls, a thick oxide layer is formed, enfolding periphery of the polysilicon sidewalls and filling the vacancy. The spacing can be alternatively retained between the polysilicon sidewalls covered with the thick oxide layer, such that the trench can be alternatively filled. The present invention is effective in increasing oxide thickness of the gate bottom, reducing the trench corner curvature as well as the feedback capacitance.

Gate fabrication method of an U-metal-oxide-semiconductor field-effect transistor and trench gate structure formed thereof

A process method for fabricating a three-dimensional source contact structure is provided, which is applicable to form a step-like three-dimensional source contact structure in a MOSFET of a power device. The proposed method sequentially adopts a lithography process and a shallow trench process to form a metal contact window. And a lateral etching process, or spacers which will be removed eventually, can be alternatively provided for increasing horizontal surface contact when depositing a source contact metal. Meanwhile, a longitudinal surface exposed by the shallow trench process is also beneficial to increase vertical contact when depositing the source contact metal. As a result, a step-like three-dimensional source contact structure can be formed by employing the present invention. It is believed that the present invention achieves in reducing cell pitch effectively and can be widely applied to various power devices having MOSFET structure thereof.

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Taipei, Taiwan

Li-Tien Hsueh