We present a planar InGaAs/InP separated absorption, grading, charge, and multiplication (SAGCM) avalanche photodiode (APD) with a thin multiplication layer of 0.2 $mu$m in thickness operating up to 10 Gb/s. It has two floating guard rings (FGRs) and a deep floating ring (DFGR). The multiplication layer thickness and the doping concentration of the charge layer are carefully designed in terms of both the gain and the bandwidth by utilizing the nonlocal model. The simple fabrication processes of recess etching and one-step diffusion are applied. The experimental results show good agreement with the design. Superior characteristics, such as a large gain-bandwidth (GB) product of above 110 GHz, a low dark current of less than 1 nA at 90 \% of the breakdown voltage, and a uniform 2-dimensional gain profile within the active region, are obtained