Abstract: A method for manufacturing a transistor of a double spacer structure is disclosed, in which a local LDD region is formed by forming a transistor including a gate electrode, and an oxide film spacer and a nitride film spacer formed sequentially, dry etching the oxide film spacer using the nitride film spacer as a mask, and injecting an impurity ion into an LDD region of a portion where the oxide film spacer is etched, short channel effect is prevented and current characteristic of the transistor is improved by combination of the ion injection process considering trade-off relation between the short channel effect and the current characteristic of the transistor during design of a device.