Process of fabricating a semiconductor device

A method for manufacturing a semiconductor device comprising the steps of:

• forming a crystalline semiconductor film over a substrate;
• irradiating a first light to improve the crystallinity of said crystalline semiconductor film;
• patterning said crystalline semiconductor film to form a semiconductor island;
• introducing a first n-type impurity element into said semiconductor island to form a first impurity region;
• irradiating a second light to activate said first n-type impurity element in said first impurity region;
• forming a gate insulating film on said semiconductor island;
• forming a gate electrode on said gate insulating film after the introduction of said first n-type impurity element so that said gate electrode partially overlaps said first impurity region with said gate insulating film interposed therebetween;
• and
• introducing a second n-type impurity element into said semiconductor island to form a second impurity region by using said gate electrode as a mask.