Method of grinding workpiece including two grinding steps

A method of grinding a workpiece to a predetermined finishing thickness, the workpiece having a first layer including a first material and a second layer including a second material that is harder to grind than the first material and stacked on the first layer, the method comprising:

• a first grinding step of grinding the first layer of the workpiece held on a chuck table with a plurality of grindstones included in a first grinding wheel and arranged in an annular array while the grinding wheel is being rotated at a first rotational speed;
• and
• a second grinding step of grinding the second layer of the workpiece held on the chuck table with the same plurality of grindstones used during the first grinding step while the first grinding wheel is being rotated at a second rotational speed that is lower than the first rotational speed,
• wherein the first grinding step is carried out after the second grinding step has been carried out, and further wherein the second grinding step is performed until the second layer has been completely removed,
• wherein the first material is silicon and the second material is silicon oxide, and
• wherein, during both the first grinding step and the second grinding step:
• the grinding wheel is moved towards the chuck table at the same predetermined speed;
• and
• the chuck table is rotated at the same predetermined rotational speed.