In this paper, we report a CMOS compatible novel penta-electrode charge-plasma diode-based optical electroabsorption modulator (EAM). The proposed integrated EAM is junctionless and employs electrostatic doping in the semiconductor to change its absorption coefficient. The proposed EAM has a vertical metal-insulator-semiconductor (MIS) and lateral metal-semiconductor (MS) junctions. Using this novel MIS-MS-based charge plasma diode, EAM with various lengths are designed on the standard 220-nm silicon-on-insulator (SOI) platform. The numerical simulations, using commercially available TCAD tools and mode solvers, are performed to estimate the performances of the proposed modulators. A couple of combinations of materials having different work functions are used as electrodes to realize this MIS-MS charge plasma diode and their performances are extensively studied. The results predict that 550 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula>-long EAM with electrodes made of palladium and aluminum offers ~ 3.4 dB of dynamic extinction ratio (ER). Approximately 8.1 dB of insertion loss (IL) will be introduced by the proposed EAM with a length of <inline-formula> <tex-math notation="LaTeX">550~\mu \text{m} </tex-math></inline-formula>. The proposed modulator is expected to provide a maximum of 30.3 GHz operating speed with 26.2 GHz of 3-dB electrooptic bandwidth. Also, the simulation result indicates that the maximum dynamic energy consumption for the proposed EAM is approximately 39.1 fJ/bit at 12.5-Gb/s data rate.