The invention refers to a method of manufacturing a semiconductor device, aiming to uniformize the thickness of a semiconductor wafer which is thinned and reduce the number of foreign matters remaining on a surface of the semiconductor wafer. The method of manufacturing a semiconductor device comprises the steps of (a) applying a resin member (3) onto a front surface of a semiconductor wafer (1) having an uneven structure (2) on the front surface thereof, and (b) flattening a surface of the resin member (3) by heating the resin member, and in the method, the resin member (3) is formed also on a side surface of the semiconductor wafer (1). The method further comprises the steps of (c) performing a thinning process for the semiconductor wafer (1) on a back surface thereof after the step (b), and (d) removing the resin member from the semiconductor wafer (3) after the step (c).