An imaging device comprising: a first semiconductor substrate including a first layer at a first side thereof, a plurality of pixel transistors (Tr1, Tr2) at the first side, and a plurality of photodiodes, wherein the first layer includes a first insulating film and a first wire; a second semiconductor substrate including a second layer at a first side thereof and a third layer at a second side thereof, wherein the second layer includes a second insulating film and a second wire, wherein the third layer includes a third insulating film and a third wire, and the second semiconductor substrate includes a first plurality of transistors (Tr6, Tr7, Tr8) between the second layer and the third layer, wherein the first and second semiconductor substrates are secured together such that the first side of the first semiconductor substrate and the first side of the second semiconductor substrate are facing each other; a third semiconductor substrate including a fourth layer at a first side thereof, and a second plurality of transistors (Tr11, Tr12, Tr13), wherein the fourth layer includes a fourth insulating film and a fourth wire, wherein the second and third semiconductor substrates are secured together such that the second side of the second semiconductor substrate and the first side of the third semiconductor substrate are facing each other; wherein the first semiconductor substrate and the second semiconductor substrate are electrically connected one another via a first conductor, wherein the first conductor penetrates the first semiconductor substrate, wherein the second semiconductor substrate and the third semiconductor substrate are electrically connected one another via a second conductor, wherein the second conductor penetrates the second semiconductor substrate; wherein a sensor circuit that corresponds to a control region and a pixel region comprising the plurality of photodiodes is formed in the first semiconductor substrate, a logical circuit is formed in the second semiconductor substrate, and a memory circuit is formed in the third semiconductor substrate; wherein a pad electrode is disposed in the second layer of the second semiconductor substrate, the pad electrode configured to be used as one end of a wire related to input and output of a signal with an external device; wherein the first conductor and the second conductor are connected to the pad electrode; and wherein the imaging device further comprises an electro-static discharge circuit, which is not provided in the first semiconductor substrate. a first semiconductor substrate including a first layer at a first side thereof, a plurality of pixel transistors (Tr1, Tr2) at the first side, and a plurality of photodiodes, wherein the first layer includes a first insulating film and a first wire; a second semiconductor substrate including a second layer at a first side thereof and a third layer at a second side thereof, wherein the second layer includes a second insulating film and a second wire, wherein the third layer includes a third insulating film and a third wire, and the second semiconductor substrate includes a first plurality of transistors (Tr6, Tr7, Tr8) between the second layer and the third layer, wherein the first and second semiconductor substrates are secured together such that the first side of the first semiconductor substrate and the first side of the second semiconductor substrate are facing each other; a third semiconductor substrate including a fourth layer at a first side thereof, and a second plurality of transistors (Tr11, Tr12, Tr13), wherein the fourth layer includes a fourth insulating film and a fourth wire, wherein the second and third semiconductor substrates are secured together such that the second side of the second semiconductor substrate and the first side of the third semiconductor substrate are facing each other; wherein the first semiconductor substrate and the second semiconductor substrate are electrically connected one another via a first conductor, wherein the first conductor penetrates the first semiconductor substrate, wherein the second semiconductor substrate and the third semiconductor substrate are electrically connected one another via a second conductor, wherein the second conductor penetrates the second semiconductor substrate; wherein a sensor circuit that corresponds to a control region and a pixel region comprising the plurality of photodiodes is formed in the first semiconductor substrate, a logical circuit is formed in the second semiconductor substrate, and a memory circuit is formed in the third semiconductor substrate; wherein a pad electrode is disposed in the second layer of the second semiconductor substrate, the pad electrode configured to be used as one end of a wire related to input and output of a signal with an external device; wherein the first conductor and the second conductor are connected to the pad electrode; and wherein the imaging device further comprises an electro-static discharge circuit, which is not provided in the first semiconductor substrate.