Further, in the case that a p-channel type TFT is used as each of the pixel switching TFTs 30, the semiconductor layer 1 a is doped with impurities, namely, elements of a III group, such as B, so as to form the low concentration source region 1 b, the low concentration drain region 1 c, the high concentration source region 1 d, and the high concentration drain region 1 e.