Patent ID: 8575620

Claim:
A circuit board, comprising: a bottom gate thin film transistor comprising a first semiconductor layer, a first gate electrode, a first source electrode, a first drain electrode, a first signal bus line, a second signal bus line, a gate-extracting line, and a source-extracting line; and a top gate thin film transistor comprising a second semiconductor layer, a second gate electrode, a second source electrode, and a second drain electrode, the first semiconductor layer and the second semiconductor layer being formed from the same material, the first drain electrode or the first source electrode and the second gate electrode being connected without interposing any other thin film transistor therebetween, and having the same electric potential, the gate-extracting line which extends from part of the first signal bus line and which is connected to the first gate electrode, and the source-extracting line which extends from part of the second signal bus line and which is connected to the first source electrode, wherein the first gate electrode and the gate-extracting line are formed from the same material, the first source electrode and the source-extracting line are formed from the same material, the first signal bus line and the gate-extracting line are formed from different materials, the first signal bus line is wider than the gate-extracting line in width, and the first signal bus line and the gate-extracting line are connected through a contact portion which penetrates an insulator at a position overlapping the first signal bus line.