Semiconductor device and manufacturing method thereof

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

• forming on a surface of a base layer a first insulating film having a flat surface;
• ion implanting a delamination material into the base layer to form a delamination layer;
• forming a plurality of light-shielding films or back gate electrodes on the surface of the first insulating film;
• forming over the surface of the first insulating film a second insulating film that covers the light-shielding films or the back gate electrodes and that has an uneven surface reflecting a stepped shape of the light-shielding films or the back gate electrodes;
• forming a dummy pattern on the surface of the second insulating film between adjoining ones of the light-shielding films or between adjoining ones of the back gate electrodes, so that a height of the dummy pattern is equal to that of the second insulating film on the light-shielding films or the back gate electrodes, as measured from the surface of the first insulating film;
• forming over the surface of the second insulating film a third insulating film that covers the dummy pattern and that has a flat surface;
• bonding the base layer provided with the third insulating film to a support substrate so that the flat surface of the third insulating film faces the support substrate;
• separating and removing along the delamination layer a part of the base layer bonded to the support substrate;
• and
• forming, from the base layer remaining over the support substrate, a plurality of semiconductor layers forming semiconductor elements, so that at least a part of the semiconductor layer overlaps the light-shielding film or the back gate electrode.