Semiconductor device and manufacturing method thereof

A manufacturing method for a semiconductor device, comprising:

• forming a transistor element on an epitaxial substrate comprising a SiC (silicon carbide) substrate and a GaN (gallium nitride) epitaxial layer formed on the SiC substrate;
• forming a multi-layer wiring structure comprising at least one metal wiring layer and an organic interlayer dielectric on a front side of the epitaxial substrate;
• grinding a back face of the epitaxial substrate;
• performing via hole etching for a back-face side of the epitaxial substrate under a condition that does not involve degradation of the organic interlayer dielectric;
• and
• plating the back face of the epitaxial substrate and a side wall of a via hole.