Semiconductor device and forming method thereof

Some embodiments provide a process for adjusting the sidewall profile of the gate opening prior to filling the replacement gate electrode layer therein, such that etch rate uniformity and stability are improved during a subsequent gate electrode etch back process. Specifically, the profile of the sacrificial gate electrode is adjusted to a straighter profile rather than a bowl-shaped profile, which reduces seam voids created in the replacement gate electrode during the replacement gate process. In some embodiments, adjusting the profile of the gate opening further includes performing a pull-back etch process of the sidewall spacers prior to depositing the gate dielectric layer and the work function metal layer, thereby achieving a wider opening for metal gate filling in a replacement gate process. The embodiment of the invention also relates to a semiconductor device and a forming method thereof. 一些实施例提供了在其中填充替换栅电极层之前调节栅极开口的侧壁轮廓的工艺，使得在随后的栅电极回蚀刻工艺期间提高蚀刻速率均匀性和稳定性。具体地，将牺牲栅电极的轮廓调整为更直的轮廓而不是碗型轮廓，这减少了在替换栅极工艺期间在替换栅电极