Disclosed is a method of manufacturing a thin film transistor device that includes the following steps: forming slanted portions 51 in edges of crystalline semiconductor films 13 (13a and 13b); forming a resist film 15 on the crystalline semiconductor film 13a so as to expose the slanted portions 51 and so as to cover the entire crystalline semiconductor film 13b; performing half exposure of the resist film 15 that is formed on the crystalline semiconductor film 13a; injecting a p-type impurity only into the slanted portions 51 of the crystalline semiconductor film 13a; removing the resist film 15 that is formed on the crystalline semiconductor film 13a by ashing; and injecting the p-type impurity into the entire crystalline semiconductor film 13a.