A thin film transistor structure for use in driving liquid crystal display elements has a semiconductor active layer, a control electrode layer underlying the active layer with an insulating layer interposed therebetween and first and second main electrode layers formed on or above the active layer in a spaced relation with each other to define a channel in the active layer in cooperation with the control electrode layer between the main electrode layers. The active layer has a first peripheral edge portion generally perpendicular to the direction of the channel and a second peripheral edge portion generally not perpendicular to the direction of the channel. The first and/or second main electrode layer extends over the first and/or second peripheral edge portion of the active layer such that at least a part of the first peripheral edge portion and/or at least part of the second peripheral edge portion of the active layer has its side face directly covered with the main electrode layer.