Semiconductor device having high voltage MOS transistor and fabrication method thereof
View Patent ↗A semiconductor device having a high voltage MOS transistor. The device includes a gate oxide layer disposed between a gate electrode and a substrate on an active area and having relatively thick portions at edges thereof. A fabrication method includes forming on the substrate is a nitride layer having an opening in a high voltage region. An oxide layer is deposited over the substrate and anisotropically etched to remain only on sidewalls of the opening. A first gate oxide layer is formed on the substrate in the opening, and the nitride layer is removed. Then a second gate oxide layer is formed over the substrate such that the second gate oxide layer has a relatively thinner thickness than the first gate oxide layer. Gate electrodes are then formed in the high voltage region and the low voltage region.
1. A method of fabricating a semiconductor device, the method comprising:
forming a field area in a semiconductor substrate so as to define an active area in a high voltage region and a low voltage region;
forming a nitride layer on the substrate, having an opening in the high voltage region;
depositing an oxide layer over the substrate;
anisotropically etching the oxide layer such that the oxide layer remains only on sidewalls of the opening;
forming a first gate oxide layer on the substrate in the opening;
removing the nitride layer;
forming a second gate oxide layer over the substrate such that the second gate oxide layer has a relatively thinner thickness than the first gate oxide layer;
forming gate electrodes in the high voltage region and the low voltage region; and
forming source/drain around the gate electrodes in the active area of the substrate.
2. The method of claim 1 , wherein the first gate oxide layer has a thickness of 500˜1500 Å and the second gate oxide layer has a thickness of 50˜300 Å.
3. The method of claim 1 , further comprising:
after the forming of the field area, forming a drift area in the substrate of the high voltage region.