Patent ID: 8143118

Claim:
A method for manufacturing a semiconductor device comprising: forming a first insulating layer over an insulating substrate; forming a first depression portion and a second depression portion with a projection portion therebetween by forming a second insulating layer over the insulating substrate; forming an amorphous semiconductor layer over the first depression portion, the second depression portion, and the projection portion; forming a crystalline semiconductor layer by melting the amorphous semiconductor layer so as to make the amorphous semiconductor layer material flow from the projection portion to the depression portions and crystallize; and forming one of a source region and a drain region and the other of the source region and the drain region in a first part and in a second part of a first region of the crystalline semiconductor layer, respectively, by adding an impurity element to the first region of the crystalline semiconductor layer without adding the impurity element to a second region of the crystalline semiconductor layer, wherein the first region of the crystalline semiconductor layer is a region where the crystalline semiconductor layer overlaps the first depression portion and the second depression portion, wherein the second region of the crystalline semiconductor layer is a region where the crystalline semiconductor layer overlaps the projection portion, wherein the first region and the second region of the crystalline semiconductor layer have a top surface substantially at a same level, and wherein the first part and the second part of the crystalline semiconductor are situated in the first depression portion and in the second depression portion, respectively.