MOS field effect pipe and its production

Abstract

The invention discloses a method for manufacturing a MOS field effect transistor. In the double gate oxide etching step, only the medium-voltage thick gate oxide in the middle part of the silicon region of the low-voltage MOS tube is etched away, and the two ends in the width direction of the MOS tube are kept close to the From somewhere within the silicon region at the junction of the shallow trench isolation region and the silicon region to a medium voltage thick gate oxide at the junction of the shallow trench isolation region and the silicon region. The invention improves the threshold voltage of the total transistor of the low-voltage MOS field effect transistor by retaining the medium-voltage thick gate oxide at the edge of the silicon region of the low-voltage MOS transistor, and improves the problem of threshold voltage drop caused by the reverse narrow channel effect of the MOS field effect transistor.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a method for manufacturing a MOS field effect transistor. Background technique [0002] In the existing process for manufacturing MOS field effect transistors, the double gate oxide etching step completely etches away the medium-voltage thick gate oxide in the entire low-voltage MOS transistor region. figure 1 It is a schematic diagram of a cross-sectional structure of a MOS field effect transistor in the prior art. Such as figure 1 As shown, there are shallow trench isolation regions on both sides of the silicon region, the gate oxide is above the gate oxide, and the polysilicon gate is above the gate oxide. The gate oxide of the MOS field effect transistor in the prior art is uniform in the width direction of the transistor. figure 2 It is a schematic diagram of a layout of a MOS field effect transistor in the prior art. Such as figure 2 As shown, in the W directio...

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Problems solved by technology

Therefore, this reverse narrow channel effect will cause the threshold voltage of the transistor to drop

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