Patent ID: 7541614

Claim:
A semiconductor device comprising: a DRAM comprising a first thin film transistor over a substrate, the first thin film transistor comprising: a first gate electrode over the substrate; a first insulating layer over the first gate electrode; a first island-shaped semiconductor film over the first insulating layer; a second insulating layer over the first island-shaped semiconductor film; a second gate electrode over the second insulating layer; and a third insulating layer over the second gate electrode; a bit line over the third insulating layer and electrically connected to a first impurity region of the first island-shaped semiconductor film; a source line over the third insulating layer and electrically connected to a second impurity region of the first island-shaped semiconductor film; a pixel portion comprising a second thin film transistor over the substrate, the second thin film transistor comprising: a second island-shaped semiconductor film over the first insulating layer; the second insulating layer over the second island-shaped semiconductor film; a third gate electrode over the second insulating layer; and the third insulating layer over the third gate electrode; a wiring over the third insulating layer and electrically connected to an impurity region of the second island-shaped semiconductor film; and a pixel electrode electrically connected to the wiring, wherein the first and second gate electrodes overlap with each other with the first island-shaped semiconductor film interposed therebetween; and wherein the substrate is selected from the group consisting of a glass substrate, a quartz substrate, a ceramic substrate, a metal substrate, and a substrate formed from a synthetic resin.