Patent ID: 8263982

Claim:
A thin film transistor comprising: a gate electrode; and a semiconductor layer including; a channel region; a source region; a drain region; a low-concentration impurity region provided between the channel region and the source or drain region, the low-concentration impurity region being doped with a first conductivity-type impurity; and a high-concentration impurity region having a higher impurity concentration than that in the channel region, the high-concentration impurity region overlapping with at least one edge portion of the gate electrode, the high-concentration impurity region being doped with a second conductivity-type impurity; wherein the semiconductor layer further includes a both conductivity-type impurity region provided between the high-concentration impurity region and the source or drain region in an area not overlapped by the gate electrode, the both conductivity-type impurity region being doped with both the first conductivity-type impurity and the second conductivity-type impurity.