Method for manufacturing semiconductor device including implanting a first impurity through an anti-oxidation mask

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

• (a) introducing a first impurity of a second conductivity type by an ion implantation in a specified region of a semiconductor substrate of a first conductivity type;
• (b) forming an oxide film on a surface of the semiconductor substrate, and diffusing the first impurity by a heat treatment in an atmosphere that does not include oxygen to form a first well of the second conductivity type;
• and
• (c) introducing a second impurity of the first conductivity type through the oxide film in a specified region of the first well, and diffusing the second impurity by a heat treatment to form a second well of the first conductivity type,
• wherein, in the stan (a), an anti-oxidation layer having a mask function against oxidation is selectively formed on the semiconductor substrate, and the first impurity is introduced in the semiconductor substrate using the anti-oxidation layer as a first mask.