This paper presents a new voice morphing method which focuses on the continuity of phonological identity overall inter- and extrapolated regions. Main features of the method are 1) to separate the characteristic of vocal tract area resonances from that of vocal cord waves by using AR-HMM analysis of speech, 2) interpolation in a log vocal tract area function domain and 3) independent morphing for the vocal tract resonances and vocal cord wave characteristics. By the morphing system constructed on a statistical conversion method, the continuity of formants and perceptual difference between a conventional method and the proposed method are confirmed.