In this work, we investigate the accumulative polarization (P) switching characteristics of ferroelectric (FE) thin films under the influence of sequential electric-field pulses. By developing a dynamic phase-field simulation framework based on time-dependent Landau-Ginzburg model, we analyze P excitation and relaxation characteristics in FE. In particular, we show that the domain-wall instability can cause different spontaneous P-excitation/relaxation behaviors that, in turn, can influence Pswitching dynamics for different pulse sequences. By assuming a local and global distribution of coercive field among the grains of an FE sample, we model the P-accumulation process in Hf 0.4 Zr 0.6 O 2 (HZO) and its dependency on applied electric field and excitation/relaxation time. According to our analysis, domain-wall motion along with its instability under certain conditions plays a pivotal role in accumulative P-switching and the corresponding excitation and relaxation characteristics.Ferroelectric (FE) materials, particularly Zr doped HfO 2 (Hf 1-x Zr x O 2 :HZO 1 ) have drawn significant research interest in recent times due to CMOS process compatibility 2 , thickness scalability 3,4 as well as many promising attributes of ferroelectric field effect transistors 2,5 (FEFETs) for low-power logic 5-8 and non-volatile memories 9,10 applications. In addition, FEFETs can provide multiple non-volatile resistive states that harness the multi-domain FE characteristics, leading to the possibilities for multi-bit synapses 11,12 in a neuromorphic hardware 13 . Further, newly reported accumulative polarization (P)-switching process 14 in ultra-thin FE leads to many appealing opportunities for novel applications like correlation detection 15 and other non-Boolean computing paradigms 16 . For such emerging applications of FEFETs, the P-switching dynamics in response to sub/super-coercive voltage pulse trains play an important role and are, therefore, critical to understand.To that effect, this letter analyzes spatially local Pswitching dynamics and its participation in globally observable P-accumulation characteristics in response to a pulse train. Our analysis is based on a dynamic phase field model 17,18 coupled with measured accumulation characteristics of HZO. By providing the spatial distribution of P (Pmap) in different electric field (E-field) excitation and relaxation steps, we discuss different types of P excitation and relaxation processes and their corresponding dependency on Efield (E) amplitude (E app max ), ON time (or excitation time T on ) and OFF time of the pulse (or relaxation time T o f f ). Finally, considering a coercive-field distribution among different FE grains, we analyze the experimental P-accumulation characteristics by utilizing our simulation framework.Let us start by describing the experimentally observed Pswitching characteristics in HZO. Fig. 1(a) shows the measured charge vs. E-field (Q-E) characteristics of a 10nm HZO film (x=0.6, grown by ALD with TiN capping layer as top and bottom contact). He...