Method for manufacturing semiconductor power device

A method for manufacturing a semiconductor device, comprising the steps of:

• forming a semiconductor element on a semiconductor wafer which includes a semiconductor layer and a semiconductor element layer on the semiconductor layer, the semiconductor element being located at a side of the semiconductor element layer;
• back-grinding evenly the semiconductor wafer from a side of the semiconductor layer to thin the semiconductor wafer, whereby the semiconductor wafer has a first thickness and a roughened ground surface of a first roughness;
• and
• thinning the semiconductor wafer by wet etching from the roughened ground surface while masking a periphery of the semiconductor wafer where no semiconductor element is disposed, whereby the semiconductor wafer has a second thickness thinner than the first thickness and a rim corresponding to the periphery where masking is disposed,
• wherein the step of thinning includes steps of removing a damaged layer formed during the back-grinding and controlling a surface roughness after the wet etching to have a processed surface of a second roughness which is different from the first roughness.