Patent ID: 8759232

Claim:
A method, comprising: exposing surface areas of a transistor of a semiconductor device to a plasma-free ammonia (NH3) and nitrogen (N2) containing atmosphere so as to prepare said surface areas for deposition of a first strain-inducing material layer; forming said first strain-inducing material layer on said surface areas using a first plasma assisted deposition process said first strain-inducing material layer inducing a compressive strain in a channel region of said transistor and having a first internal stress level; wherein the first plasma assisted deposition process comprises: (a) providing an initial process atmosphere comprising an initial flow rate of carrier gas of zero or higher at a low frequency power of from 30-150 W for a deposition time of about 15 seconds, and, (b) performing: (i) a first transition step comprising supplying a high frequency power of from about 60-160 W, the ratio of high frequency power to low frequency power being in the range of 1.5-2.5, and (ii) a second transition step comprising increasing the flow rate of carrier gas while maintaining said high frequency power for a time of 72-110 seconds; and forming a second strain-inducing material layer on said first strain-inducing material layer by using a second plasma assisted deposition process, said first plasma assisted deposition process differing from said second plasma assisted deposition process by at least one process parameter setting, said second strain-inducing material layer inducing a compressive strain in said channel region and having a second internal stress level that is higher than said first internal stress level.