Semiconductor device and manufacturing method thereof

Abstract

A semiconductor device includes a semiconductor layer and a deep trench structure. The deep trench structure includes a deep trench, a first shallow trench, and a second shallow trench sequentially disposed from bottom to top. The first shallow trench includes a first bottom opening and a first top opening. The first bottom opening is located on a first plane and connects to the deep trench. The first top opening is located on a second plane, and the width of the first bottom opening is smaller than the width of the first top opening. The second shallow trench also includes a second bottom opening and a second top opening. The second bottom opening is located on a second plane and connects to the first shallow trench. The second top opening is adjacent to the top surface of the semiconductor layer, and the width of the second bottom opening is smaller than the width of the second top opening. The width of the first top opening of the first shallow trench is not greater than the width of the second bottom opening of the second shallow trench.