Disclosed is a TSV structure having insulating layers with embedded voids, including a chip layer, a dielectric liner and a conductive filler. There is at least a via reentrant from one surface of the semiconductor body of the chip layer. A plurality of air-gap cavities are formed on the sidewall of the via where the cavities have a depth-to-width ratio not less than one. The dielectric liner covers the sidewall of the via without filling into the air-gap cavities. The conductive filler is disposed in the via without filling into the air-gap cavities due to the isolation of the dielectric liner so as to form an air insulating layer with a plurality of enclosed voids embedded between the semiconductor body and the dielectric liner. Accordingly, RC Delay of the TSV structure can be improved.