Manufacturing method for semiconductor device

A method for manufacturing a semiconductor device, comprising:

• forming a semiconductor layer;
• forming a gate insulating film on the semiconductor film;
• forming a first conductive layer over the gate insulating film;
• forming a second conductive layer on the first conductive layer;
• forming a third conductive layer on the second conductive layer;
• etching the first conductive layer, the second conductive layer, and the third conductive layer to form a first conductive-layer pattern;
• selectively etching the second conductive layer and the third conductive layer in the first conductive-layer pattern with plasma of boron trichloride, chlorine, and oxygen to form a second conductive-layer pattern;
• and
• forming a first impurity region and a second impurity region in the semiconductor layer.

A method for manufacturing a semiconductor device, comprising:

• forming a semiconductor layer;
• forming a gate insulating film on the semiconductor film;
• forming a first conductive layer over the gate insulating film;
• forming a second conductive layer on the first conductive layer;
• etching the first conductive layer and the second conductive layer to form a first conductive-layer pattern;
• selectively etching the second conductive layer in the first conductive-layer pattern with plasma of boron trichloride, chlorine, and oxygen to form a second conductive-layer pattern;
• and
• doping the semiconductor layer with an impurity element through the first conductive layer in the second conductive-layer pattern to form an LDD region.

A method for manufacturing a semiconductor device, comprising:

• forming a semiconductor layer;
• forming a gate insulating film on the semiconductor film;
• forming a first conductive layer over the gate insulating film;
• forming a second conductive layer on the first conductive layer;
• forming a third conductive layer on the second conductive layer;
• etching the first conductive layer, the second conductive layer, and the third conductive layer to form a first conductive-layer pattern;
• selectively etching the second conductive layer and the third conductive layer in the first conductive-layer pattern with plasma of boron trichloride, chlorine, and oxygen to form a second conductive-layer pattern;
• and
• doping the semiconductor layer with an impurity element through the first conductive layer in the second conductive-layer pattern to form an LDD region.