Semiconductor device
A highly reliable semiconductor device the yield of which can be prevented from decreasing due to electrostatic discharge damage is provided. A semiconductor device is provided which includes a gate electrode layer, a first gate insulating layer over the gate electrode layer, a second gate insulating layer being over the first gate insulating layer and having a smaller thickness than the first gate insulating layer, an oxide semiconductor layer over the second gate insulating layer, and a source electrode layer and a drain electrode layer electrically connected to the oxide semiconductor layer. The first gate insulating layer contains nitrogen and has a spin density of 1×10 17 spins/cm 3 or less corresponding to a signal that appears at a g-factor of 2.003 in electron spin resonance spectroscopy. The second gate insulating layer contains nitrogen and has a lower hydrogen concentration than the first gate insulating layer.
1. A method for manufacturing a semiconductor device, comprising:
forming a gate electrode over a substrate;
forming a first gate insulating layer including nitrogen after forming the gate electrode;
forming a second gate insulating layer including nitrogen after forming the first gate insulating layer;
forming an oxide semiconductor layer after forming the second gate insulating layer; and
forming a source electrode and a drain electrode electrically connected to the oxide semiconductor layer,
wherein the second gate insulating layer has a lower hydrogen concentration than the first gate insulating layer, and
wherein a content of indium is higher than a content of gallium in the oxide semiconductor layer that is closer to the gate electrode, and a content of indium is lower than or equal to a content of gallium in the oxide semiconductor layer that is farther from the gate electrode.
2. The method for manufacturing a semiconductor device according to claim 1 , wherein the first gate insulating layer is formed by a mixed gas of silane, nitrogen and ammonia, and the second gate insulating layer is formed by a mixed gas of silane and nitrogen.
3. The method for manufacturing a semiconductor device according to claim 1 , wherein the first gate insulating layer has a spin density of 1×10 17 spins/cm 3 or less corresponding to a signal that appears at a g-factor of 2.003 in electron spin resonance spectroscopy.
4. The method for manufacturing a semiconductor device according to claim 1 , wherein the first gate insulating layer has fewer defects than the second gate insulating layer.
5. A method for manufacturing a semiconductor device, comprising:
forming a gate electrode over a substrate;
forming a first gate insulating layer including nitrogen after forming the gate electrode;
forming a second gate insulating layer including nitrogen after forming the first gate insulating layer;
forming an oxide semiconductor layer after forming the second gate insulating layer; and
forming a source electrode and a drain electrode electrically connected to the oxide semiconductor layer,
wherein the second gate insulating layer has a lower hydrogen concentration than the first gate insulating layer,
wherein the first gate insulating layer is thicker than the second gate insulating layer, and
wherein a content of indium is higher than a content of gallium in the oxide semiconductor layer that is closer to the gate electrode, and a content of indium is lower than or equal to a content of gallium in the oxide semiconductor layer that is farther from the gate electrode.
6. The method for manufacturing a semiconductor device according to claim 5 , wherein the first gate insulating layer is formed by a mixed gas of silane, nitrogen and ammonia, and the second gate insulating layer is formed by a mixed gas of silane and nitrogen.
7. The method for manufacturing a semiconductor device according to claim 5 , wherein the first gate insulating layer has a spin density of 1×10 17 spins/cm 3 or less corresponding to a signal that appears at a g-factor of 2.003 in electron spin resonance spectroscopy.
8. The method for manufacturing a semiconductor device according to claim 5 , wherein the first gate insulating layer has fewer defects than the second gate insulating layer.
9. A method for manufacturing a semiconductor device, comprising:
forming a gate electrode over a substrate;
forming a first gate insulating layer including nitrogen after forming the gate electrode;
forming a second gate insulating layer after forming the first gate insulating layer;
forming an oxide semiconductor layer after forming the second gate insulating layer; and
forming a source electrode and a drain electrode electrically connected to the oxide semiconductor layer,
wherein a content of indium is higher than a content of gallium in the oxide semiconductor layer that is closer to the gate electrode, and a content of indium is lower than or equal to a content of gallium in the oxide semiconductor layer that is farther from the gate electrode.
10. The method for manufacturing a semiconductor device according to claim 9 , wherein the first gate insulating layer is formed by a mixed gas of silane, nitrogen and ammonia, and the second gate insulating layer is formed by a mixed gas of silane and nitrogen.
11. The method for manufacturing a semiconductor device according to claim 9 , wherein the first gate insulating layer has a spin density of 1×10 17 spins/cm 3 or less corresponding to a signal that appears at a g-factor of 2.003 in electron spin resonance spectroscopy.
12. The method for manufacturing a semiconductor device according to claim 9 , wherein the first gate insulating layer has fewer defects than the second gate insulating layer.