Characterization and modeling of threshold voltage shift due to quantum mechanical effects in pMOSFET

The threshold voltage shift due to quantum mechanical effects (QMEs) has su bstantial influences on modern pMOSFET characteristics. Investigations of Q MEs in a pMOSFET are classified into two approaches: full-band calculation and effective mass approximation. In this paper, formulation of carrier dis tribution in the pMOSFET inversion layer in the threshold region based on t he effective mass approximation is presented, and a new method to calculate the threshold voltage shift due to QMEs is developed. The results with the effective mass approximation are compared with the full-band calculation a nd show satisfactory coincidence. Based on the present model, the subband s tructure of the hole inversion layer and the earlier distribution character istics are investigated. The quantum mechanical and semi-classical two-dime nsional density of states (2D DOS) are calculated and compared. The depende nce of the threshold voltage shift due to QMEs on substrate doping concentr ation is then analyzed from the DOS point of view. (C) 2000 Elsevier Scienc e Ltd. All rights reserved.