A substrate structure and a semiconductor package structure are provided. The substrate structure includes a first dielectric layer, a pad and a conductive structure. The first dielectric layer has a first surface and a second surface opposite to the first surface. The pad is adjacent to the first surface and at least partially embedded in the first dielectric layer. The first dielectric layer has an opening exposing the pad, and a width of the opening is less than a width of the pad. The conductive structure is disposed on the pad and composed of a first portion outside the opening of the first dielectric layer and a second portion embedded in the opening of the first dielectric layer. The first portion has an aspect ratio exceeding 1.375.