An active layer of an NTFT includes a channel forming region, at least a first impurity region, at least a second impurity region and at least a third impurity region therein. Concentrations of an impurity in each of the first, second and third impurity regions increase as distances from the channel...http://www.google.ca/patents/US6784037?utm_source=gb-gplus-sharePatent US6784037 - Semiconductor device and manufacturing method therefor
