Method for increasing length of effective channel of PMOS

Abstract

The invention provides a method for increasing the length of an effective channel of a PMOS, which comprises the following steps of: making an n-well and a p-well in a substrate; making a first polysilicon gate on the n-well and making a second polysilicon gate on the p-well; growing a first oxidation layer; injecting lightly doped source / drain in an n-well area; respectively growing a second oxidation layer on the surface of the n-well and the p-well; injecting lightly doped source / drain in a p-well area; respectively growing a silicon nitride layer and a third oxidation layer in the n-well and the p-well areas; etching the first oxidation layer, the second oxidation layer, the silicon nitride layer and the third oxidation layer; respectively forming a side wall around the polysilicon gates of the n-well and the p-well; injecting heavily doped source / drain in the n-well area; and injecting heavily doped source / drain in the p-well area. The method moves the step of injecting the lightly doped source / drain in the p-well area between the step of growing the second oxidation layer and the step of growing the silicon nitride layer and increases the length of the effective channel of the PMOS by using the second oxidation layer.

Description

technical field [0001] The invention belongs to a semiconductor process, in particular to a method for increasing the effective channel length of PMOS. Background technique [0002] At nodes below the 90nm process, due to the reduction of the gate feature size (for example, 65nm), severe short channel effects are caused, and the leakage current of the device increases sharply. The short-channel effect is that the threshold voltage of the MOSFET decreases as the channel length decreases. If an operating voltage is applied to the drain, the short channel effect will be exacerbated. The result of the short channel effect is to increase the leakage current of the device. In the CMOS VLSI process, the channel length will vary due to the process. Therefore, short-channel effects are a very important consideration in device design. We have to make sure that the threshold voltage of the smallest channel size in a chip is not too low. [0003] When the voltage applied to the sou...

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Problems solved by technology

[0007] The technical problem to be solved by the present invention is to provide a method to solve the problem of short channel effect in PMOS

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