This paper reports with details on the characterization and nonlinear modeling steps of an integrated structure developed and patented by ACCO Semiconductor termed as MASMOS that is particularly well suited for radio frequency power amplifier integration for handset applications. From I-V and S-parameters measurements, a large signal electrical model of two different MASMOS structures was derived. A conventional three-port electrical approach has been used and proved viable to model the large signal performances (e.g., prediction of loci of fundamental and harmonic load impedances for maximum efficiency or output power operations) of the device. Compared with the already existing in-house MASMOS physical model, the proposed compact modeling approach gives very comparable results while being more computationally efficient, giving a significant simulation time saving in a RF power amplifier design-flow perspective.