| R2R | Run-to-run |
| Ra | Radium |
| RAC | Remote Access And Control |
| RAE | Residue After Evaporation |
| RAHU | Recirculation Air Handling Unit |
| RAIRS | Reflection-absorption Infrared Spectroscopy |
| RAM | Random Access Memory |
| RAM | Reliability, Availability, And Maintainability |
| RAMP | Reliability Analysis And Modeling Program |
| Rb | Rubidium |
| RBA | Rotary Bonded Abrasive |
| RBB | Base Sheet Resistance |
| RBC | Radiation Boundary Condition |
| RBMT | Region-based Multi-thresholding |
| RBS | Refractive Backscattering |
| RBS | Rutherford Backscattering Spectroscopy |
| RBV | Ramp Breakdown Voltage |
| RC | Resistance-capacitance |
| RCE | Rotating Compensator Ellipsometer |
| RCS | Revision Control System |
| RCT | Reference Cluster Tool |
| RCWA | Rigorous Coupled Wave Analysis |
| RDLY | Random Limited Yield |
| RDMT | Radio, Dispatch, Mobile Data, Transportation Management |
| RDR | Rotating Disk Reactor |
| RDS | Remote Dispense System |
| RDS | Resist Dispense System |
| Re | Rhenium |
| REL | Recommended Exposure Limit |
| RESSFOX | Recessed Sealed Sidewall Field Oxidation |
| RET | Resolution Enhancement Technique |
| RF | Radio Frequency |
| RF | Resonance Frequency |
| RFI | Request For Information |
| RFI | Radio Frequency Interference |
| RFM | Radio Frequency Monitoring |
| RFO | Restricted Flow Orifice |
| RFP | Request For Plan |
| RFP | Request For Proposal |
| RFP | Radio Frequency Probe |
| RFQ | Request For Quote |
| RFT | Resonant Frequency Tool |
| RGA | Residual Gas Analysis |
| RGV | Rail Guided Vehicle |
| Rh | Rhodium |
| RH | Relative Humidity |
| RI | Reliability Improvement |
| RIE | Reactive Ion Etch |
| RIM | Read-in Mode |
| RISC | Reduced Instruction Set Computer/computing |
| RIST | Rule Induction And Statistical Testing |
| RLI | Resist Lithography |
| RMI | Remote Method Invocation |
| RMOS | Refractory Metal-oxide Semiconductor |
| RMS | Root Mean Square |
| RMS | Recipe Management Standard |
| RMS | Reticle Management System |
| RMS | Reference Management System |
| RMSEP | Root Mean Square Error Of Prediction |
| RMTF | Recipe Management Task Force |
| Rn | Radon |
| RNN | Recurrent Neural Network |
| RO | Reverse Osmosis |
| ROC | Remote Object Communications |
| ROE | Return On Equity |
| ROI | Return On Investment |
| ROM | Read-only Memory |
| ROMP | Ring Opening Metathesis Polymerization |
| ROX | Run Of Experiments |
| RPAO | Remote Plasma Assisted Oxidation |
| RPC | Remote Procedure Call |
| RPD | Relative Percent Deviation |
| RPECVD | Rapid Plasma-enhanced Chemical Vapor Deposition |
| RPN | Remote Plasma Nitridation |
| RPS | Relative Phase Shift |
| RQ | Reportable Quantity |
| RR | Removal Rate |
| RRMSEP | Relative Root Mean Square Error Of Prediction |
| Rs | Sheet Resistance |
| RSCE | Reverse Short Channel Effect |
| RSE | Reactive Sputter Etch |
| RSF | Relative Sensitivity Factor |
| RSM | Response Surface Methodology |
| RSM | Response Surface Matrix |
| RSM | Reciprocal Space Map |
| RSP | Reticle Standard Pod |
| RT | Room Temperature |
| RTA | Rapid Thermal Anneal |
| RTB | Real-time Backplane |
| RTC | Resist Test Center |
| RTCVD | Rapid Thermal Chemical Vapor Deposition |
| RTD | Resistance Temperature Detector |
| RTE | Radiation Transport Equation |
| RTL | Resistor-transistor Logic |
| RTL | Register Transfer Level |
| RTM | Rapid Thermal Multiprocessing |
| RTO | Rapid Thermal Oxidation |
| RTO | Regenerative Thermal Oxidizer |
| RTP | Rapid Thermal Processing (or Processor) |
| RTR | Real-time Reporting |
| RTS | Request To Send |
| RTSPC | Real-time Statistical Process Control |
| RTV | Room Temperature Vulcanizing |
| RTY | Retry Limit |
| Ru | Ruthenium |
| RVB | Ramped Voltage Breakdown |
| RZ | Return To Zero |