A semiconductor structure and a method of fabricating thereof are provided. The semiconductor structure includes a substrate and a capacitor structure. The substrate has a first blind hole and a trench. The first blind hole communicates with the trench. The first blind hole has a first depth, and the trench has a second depth smaller than the first depth. The capacitor structure includes a first inner conductor, a first inner insulator, and an outer conductor. The first inner conductor is in the first blind hole. The first inner insulator surrounds the first inner conductor. The outer conductor has a first portion surrounding the first inner insulator and an extending portion extending from the first portion. The first portion is in the first blind hole, and the extending portion is in the trench. The first inner conductor is separated from the outer conductor by the first inner insulator.