Method for manufacturing semiconductor device

The invention discloses a method for manufacturing a semiconductor device, which includes forming a first oxide layer on a high-voltage region and a low-voltage region; performing an atomic layer deposition manufacturing process to form a second oxide layer on the first oxide layer, wherein the power of the atomic layer deposition manufacturing process is between 50 and 400 watts; performing an annealing manufacturing process having a temperature between 80 and 500 degrees Celsius; removing a portion of the first oxide layer and a portion of the second oxide layer covering the low-voltage region; forming a third oxide layer on the high-voltage region and the low-voltage region; and forming a gate structure on the high-voltage region and the low-voltage region to form a high-voltage transistor and a low-voltage transistor. The method can reduce the ion accumulation caused by the atomic layer deposition manufacturing process, thereby avoiding catalysis of substrate damage in subsequent manufacturing process ste